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The role of β-endorphins and catechol estrogens on the hypothalamic-pituitary axis in female athletes*
Vol. 42, No.5, November 1984 Printed in U.8A.
FERTILITY AND STERILITY Copyright < 1984 The American Fertility Society
The role of ~-endorphins and catechol estrogens on the hypothalamic-pituitary axis in female athletes*
Jeffrey B. Russell, M.D.t Dorothy E. Mitchell, M.D. t Paull. Musey, Ph.D.:j: Delwood C. Collins, Ph.D.:j:§ Emory University School of Medicine, Veterans Administration Medical Center, Atlanta, Georgia
Competitive swimmers were followed over a 2 -year period when they trained at different levels of exercise which coincided with distinct changes in their menstrual history. Oligomenorrhea was identified in 5 of 13 of these athletes when they swam approximately 100,000 yards per week. Weight and percentage of body fat were not significantly different between the period of oligomenorrhea and regular menstrual function (P = 0.24). Mean and median levels of luteinizing hormone, folliclestimulating hormone, prolactin, and 17f3-estradiol were decreased and catechol estrogens and J3-endorphins were increased in serum during the strenuous, when compared with the moderate, training period. The serum levels of the steroid and protein hormones were similar to those of normal cycling, nonexercising control subjects during moderate exercise (60,000 yards per week). The significant differences between J3-endorphins and catechol estrogens during periods of strenuous exercise suggest an explanation lor oligomenorrhea in female athletes. These hormonal changes result in hypothalamic anovulation, which appears to be reversible, because the hormone levels and menstrual cycles return to normal when the exercise is reduced. Fertil Steril 42:690, 1984
Numerous studies have been initiated to investigate the relationship between physical activity and menstrual dysfunction. 1-8 The etiology of this menstrual dysfunction is not completely understood. Delayed menarche, luteal phase defects, and decreased levels of luteinizing hormone (LH), Received May 14, 1984; revised and accepted July 25, 1984. *Supported in part by the National Institutes of Health grant NIH-1-R01-AG-02012 and Veterans Administration Project 7176-001. tDepartment of Gynecology and Obstetrics. tDepartment of Medicine. §Reprint requests: Delwood C. Collins, Ph.D., Medical Research Service, VA Medical Center, 1670 Clairmont Road, Decatur; Georgia 30033. 690
Russell et al. Exercise and oligomenorrhea
follicle-stimulating hormone (FSH), prolactin (PRL), 1713-estradiol (E 2 ), and progesterone have been confirmed in marathon runners and ballet dancers. Previous clinical studies have implicated rapid weight loss, decreased percentage of body fat, prior menstrual dysfunction, stress, age at onset of training, and amount of training as key factors. Strenuous exercise on a regular basis has been shown to increase l3-endorphins (I3-EP),8 catecholamines,7 and catechol estrogens9 in women. Individually, catechol estrogens have been shown to decrease the basal levels ofLH. lO Catecholamines have been implicated in the regulation of gonadotropin-releasing hormone (GnRH) release from Fertility and Sterility
the median eminence of the hypothalamus. 11 The role of [3-EP in LH release has been investigated in normal subjects. 12 All of these studies implicate [3-EP as responsible for a significant decline in the concentration of LH. The purpose of this study was to determine the relationship between menstrual dysfunction and basal levels of several hormones in the same women during different levels of exercise. These differences were correlated with changes in the menstrual cycle history and give new information about the effect of different levels of exercise on menstrual dysfunction in female athletes.
MATERIALS AND METHODS
Thirteen swimmers from the Dynamo Swim Club of Atlanta, Georgia, were studied during the peak of their training in December 1981 through January 1982 and again from December 1982 through January 1983. The training period in December 1981 (strenuous) consisted of a gradual increase in physical activity until the athletes were swimming 100,000 yards per week. Five swimmers became oligomenorrheic during this period. This peak level of training was followed by a reduction in training to 30,000 yards per week by March 1982. Normal menstrual function returned during this period. Between September 1982 and April 1983, these five swimmers increased their exercise level to 60,000 yards per week in January 1983 and continued to show normal menstrual cycles. The intensity of the training sessions can be defined as swimming 16,000 yards (100,000 yards per week) or 10,000 yards (60,000 yards per week) in a 6-hour period. Thus, the menstrual history and normal pattern of five swimmers were assessed and compared during different levels of exercise. The five swimmers served as their own controls. Six women who did not participate in any organized physical activity, who had a history of normal menstrual cycles, were also used as controls. All participants completed a questionnaire pertaining to age, menarche, menstrual history, parity, height, weight, and oral contraceptive history. Athletes with a history of irregular menses or prior menstrual dysfunction were excluded from the study. Menstrual history was recorded from May 1981 to April 1983. Oligomenorrhea was defined as 60 days or more without a menstrual period" after a minimum of 3 months of Vol. 42, No.5, November 1984
regular cycles. Regular cycles were defined as menses every 27 to 34 days. The swimmers recorded weekly weights along with a log of their exercise. Serum samples were taken from the control subjects between days 13 and 17 of their menstrual cycle. Serum samples were taken from the athletes 30 minutes prior to exercise during both training periods. Serum samples were analyzed for FSH, LH, PRL, E 2, and catechol estrogens by procedures established in this laboratory.13 FSH and LH were measured by radioimmunoassay (RIA) using kits obtained from Radioimmunoassay Systems Laboratories, Carson City, CA. The intraassay coefficients of variation for LH, FSH, and PRL were between 6.8% and 10.2%. The interassay coefficients of variation for these assays varied between 8.1% and 12.8%. [3-EP immunoreactivity and PRL were measured using RIA kits from Immunonuclear Corporation, Stillwater, MN. This is a measure of [3-EP immunoreactivity because the [3-lipotropins have some affinity (= 20%) for this antiserum, and [3-lipotropin fractions cannot be excluded. The intraassay and interassay coefficients of variation for [3-EP were 7.5% and 13.5%, respectively. E2 was measured by RIA with standard procedures developed in this laboratory.13 This antiserum is specific for E2 and shows no significant cross-reaction for other estrogens. Catechol estrogens were determined by RIA using specific antibodies developed against 2-hydroxyestrone-6carboxymethyl oxime as previously described. 14 This antibody cross-reacts almost 100% with 2hydroxyestradiol. Thus, the values measured here reflect catechol estrogen levels. The intraassay and interassay coefficients of variation were 3.8% and 4.6%, respectively, for the catechol estrogens, and 4.9% and 6.3%, respectively, for E 2. The percentage of body fat was determined for each subject. This was obtained from the skinfold thickness measurement using constant-tension Lange skinfold calipers at two sites. One measurement was obtained from the area slightly oblique just above the hipbone in the midaxillary line, and the second from the back of the arm at the midpoint between the acromion and the olecranon processes. The triceps and suprailiac measurements were used to calculate the body density with a standard error of estimation for the equation being ± 0.0082 gm/ml. The percentage of body fat was calculated with the nomogram described by Sloan and Weir.15 Russell et al. Exercise and oligomenorrhea
691
Table 1. Statistical Summary (Mean ± SD with Range in Parentheses) and Analysis ofPhysical Characteristics for the Swimmers During Periods of Moderate and Strenuous Exercise and the N onexercising Control Subjects Swimmers Physical characteristics Age (yr) Weight (kg) Height (in) Menarche ('" 12/;;. 13) % Body fat
Cycle dayc
Control subjects 19.0 ± 1.7 (18--22) 50.6 ± 5.0 (43.1--57.2) 63.0 ± 2.4 (60-66) 5/1 (11-13) 18.8 ± 1.8 (16.2-21.3) 14 (13--18)
Moderate (60,000 yards)
51.8 ± 2.3 (49.4--55.3) 64.2 ± 1.6 (62-66) 17.9 ± 1.7 (15.5-19.6) 15 (3-25)
Strenuous (100,000 yards) 14.4 ± 2.0 (13-17) 48.5 ± 2.1 (46.3--51.3) 63.4 ± 1.8 (61-65) 114 (12-15) 17.4 ± 2.1 (14.6-20.0) 105 (66-116)
Group comparison C vs. 60
C vs. 100a
100 vs. 60b
P = 0.009
P = 0.002
P = 0.66
P = 0.66
P = 0.004
P = 0.36
P = 0.76
P = 0.016
P = 0.42
P = 0.26
P = 0.24
P = 0.054
P = 0.004
P«
0.10
aTwo independent group t-test, Mann-Whitney U-test, or Fisher's exact test. bpaired t-test or Wilcoxon signed rank test. cSample median with range in parentheses.
RESULTS Five competitive swimmers and six control subjects recorded menstrual logs between May 1981 and April 1983. The five swimmers studied had oligomenorrhea for at least 64 to 116 days prior to the time serum samples were taken for steroid and protein analyses. The median cycle dates for collection of blood samples for hormone analysis are shown in Table 1. The mean value (± standard deviation [SD]) for the physical characteristics of the participants are shown in Table 1: All participants were between 13 and 22 years of age. The mean age (± SD) of the swimmers during the period of strenuous exercise was 14.4 ± 2.0 years (range, 13 to 17). The mean age of the control group was significantly higher (19.0 ± 1.7; range, 18 to 22 years; P« 0.01). The mean age of menarche (± SD) in the athletes was 13.5 ± 1.0 years (range, 12 to 15) and was not significantly different from that of the control group (11.8 ± 0.7 years; range, 11 to 13). However, five of six control subjects showed menarche by age 13, compared with only one of five swimmers. The mean body weight (± SD) of the swimmers was 48.5 ± 2.1 kg (range, 46.3 to 51.3) in 1982, during the period of strenuous exercise, and 51.8 ± 2.3 kg (range, 49.4 to 55.3) in 1983, during the period of moderate exercise. The mean weight (± SD) for the control group was 50.6 ± 5.0 kg (range, 43.1 to 57.2). The mean percentage of body fat (± SD) for the swimmers during the period of strenuous exercise (17.4 ± 2.1) was not significantly different from that in 692
Russell et al. Exercise and oligomenorrhea
the moderate exercise period (17.9 ± 1.7). Furthermore, the mean percentage of body fat in the control group was not significantly different from that of the swimmers in either time period (P = 0.42; P = 0.26). The mean and median levels of protein hormones were determined in the swimmers at the two different levels of exercise (Table 2). The median serum LH value for the swimmers during the period of strenuous exercise was significantly lower (11.3 mIUlml) than that for the same individuals during moderate exercise (22.2) (P = 0.02). The median LH value during the period of moderate exercise was not significantly different from that in the control group (21.4; P = 0.66). A similar pattern was seen when the mean LH values were compared. The median level of FSH was significantly lower in swimmers during the period of strenuous exercise (6.8 mIU/ml) when compared with the moderate exercise period (18.2; P « 0.001). The median level ofFSH in the control group (9.6) was intermediate between and significantly different from those in the swimmers during the two periods of exercise. A similar pattern was seen when the mean values were compared. The median serum level for PRL was suppressed to 1.0 ng/ml in the swimmers during strenuous exercise. This was significantly lower than the level during moderate exercise (P = 0.006) as well as that in the control subjects (P = 0.004). The median level of PRL during the moderate exercise period was not significantly differFertility and Sterility
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Table 2. Statistical Summary (Mean [Median) ± SD with Range in Parentheses} and Analysis of Protein Hormones for the
Swimmers During Periods of Moderate and Strenuous Exercise and the Nonexercising Control Subjects Swimmers Hormone
Control subjects
Moderate
No.
(100,000 yards)
6 5 23.1 [21.4] ± 10.5 22.9 [22.2] ± 5.7 m!) (12.3-43.3) (15.9-30.7) 10.9 [9.6] ± 3.5 20.2 [18.2] ± 5.1 FSH (mIU/ m!) (7.1-15.7) (15.3-27.7) PRL (ng/m!) 20.8 [13.5] ± 15.0 10.6 [10.5] ± 3.6 (9.0-47.2) (5.9-16.1)
LH (mIU/
Group comparison (median values)
Strenuous
(60,000 yards)
5 10.9 [11.3] ± 2.8 (7.4-13.6) 6.54 [6.8] ± 2.1 (4.0-9.5) 1.36 [1.0] ± 0.9 (0.7-3.0)
ent from that in the control group (P = 0.18). A similar pattern was seen when the mean values were compared. The mean and median levels of E2 and catechol estrogens are shown in Table 3. The median E2 level during the period of strenuous exercise (52 pg/mD was not significantly different from that during moderate exercise (65 pg/ml) (P = 0.68). The median levels for the swimmers during both periods of exercise were significantly lower than in the control subjects. A similar pattern was seen when the mean values for E2 were compared. The median levels of catechol estrogens were similar for the control group and the swimmers during moderate exercise (median, 35 and 28; P = 0.08). During strenuous exercise, the swimmers had significantly higher levels of catechol estrogens (median, 88; P < < 0.001). A similar pattern was seen when mean levels of catechol estrogens were compared. The median levels of I3-EP immunoreactivity (Table 3) were also significantly higher in the swimmers during their strenuous exercise period when compared with moderate exercise or the control values. The median control value was not significantly different from that of the swimmers during moderate exercise.
C vs. 60
C vs. 100
100 vs. 60
P
=
0.66
P
=
0.02
P
P
=
0.05
P
=
0.04
P «
0.001
P
=
0.18
P
=
0.004
P
0.006
=
0.02
=
DISCUSSION
Oligomenorrhea with or without changes in body fat is well documented in athletes. 16 Our results suggest that oligomenorrhea can occur without a change in the percentage of body fat in swimmers and do not support results from other laboratories which suggest a critical percentage of body fat for the onset and mairitenance of menses. 17 Thus, the clinical recommendation commonly made to these athletes to gain weight may not resolve their oligomenorrhea. Our data suggest that the level or intensity of exercise may be more critical in the transient cessation of menstrual function. The endogenous levels of catechol estrogens were elevated in the swimmers during the period coinciding with strenuous exercise. The values for catechol estrogens in the swimmers on moderate exercise and in the control subjects were similar to those previously reported. 18, 19 This is the first time that a correlation has been made between increased levels of catechol estrogens and oligomenorrhea in the same individuals. Because each subject at the moderate exercise level with normal menstrual cycles serves as her own control, the importance of the control group is greatly
Table 3. Statistical Summary (Mean [Median) ± SD with Range in Parentheses} and Analysis off3-EP Immunoreactivity, E 2 , and
Catechol Estrogens for Swimmers During Periods of Moderate and Strenuous Exercise and the Nonexercising Control Subjects Control subjects
Hormone No. E2 (pg/ml) Catechol estrogens (pg/ml) f3-EP immunoreactivity (pmol/!)
Swimmers Moderate
(60,000 yards)
6 5 264 [193] ± 253 61.8 [65] ± 16.8 (78-759) (36-79) 35.3 [35] ± 7.5 28.0 [28] ± 1.2 (25-46) (26-29) 8.50 [2] ± 15.4 4.40 [4] ± 2.2 (2-40) (2-8)
Vol. 42, No.5, November 1984
Group comparisons
Strenuous (100,000 yards) 5 76.8 [52] ± 61.9 (36-185) 92.4 [88] ± 12.8 (83-115) 31.2 [24] ± 14.3 (18-52)
C vs. 60
C vs. 100
P
=
0.009
P
P
=
0.08
P «
P
=
0.25
P
=
=
0.003 0.001 0.03
100 vs. 60
P
=
0.68
P« P
=
0.001 0.01
Russell et a1. Exercise and oligomenorrhea
693
reduced. Recent studies of the physiologic role of catechol estrogens indicate that they may reduce the rate of degradation of catecholamines by catechol-O-methyltransferase (COMT), thus increasing the availability of catecholamines for biologic action in the hypothalamus. 2o The competition with catechol estrogens for COMT, along with the elevation of catecholamines during exercise, may lead to the suppression of GnRH and PRL by dopamine. 21 The first evidence for an effect of [3-EP on gonadotropin release was shown by Barraclough and Sawyer, 22 who reported that ovulation was blocked by an analog of [3-EP, morphine sulfate, in rats. Kalra and Simpkins23 showed that [3-EP binds to hypothalamic cells which secrete GnRH and blocks GnRH rel-ease by norepinephrine. Our results suggest that [3-EP levels were significantly higher in the swimmers during periods of strenuous exercise when compared with moderate exercise. This is the first time that [3-EP have been measured and shown to be correlated with distinct changes associated with exercise and oligomenorrhea in the same individuals. It should be noted, however, that the [3-EP assay used in this study measures immunoreactivity. Thus, cross-reaction with [3-lipotropin fractions cannot be excluded. The significant differences between catechol estrogens and [3-EP during periods of moderate or strenuous exercise suggest an explanation for oligomenorrhea in female athletes. Increased levels of [3-EP, catechol estrogens, and dopamine during strenuous exercise may interact to cause suppression of GnRH release, either directly or indirectly. Our results suggest that the elevated catechol estrogens may compete with catecholamines for COMT, leading to decreased degradation of dopamine and increased inhibitory effect of dopamine on GnRH. The decreased basal levels of PRL seen in swimmers during strenuous exercise may reflect this elevated dopamine level. Furthermore, the stimulatory effect of norepinephrine on GnRH may be inhibited by the increased level of [3-EP which bind to norepinephrine receptors in the hypothalamus, leading to a suppression of LH and FSH. These hormonal changes result in hypothalamic anovulation which appears to be reversible, because the hormone levels return to normal when the level of exercise is reduced. Acknowledgments. We thank Mr. Pat Hogan, Coach, and members of the Atlanta Dynamo Club, Dr. Ray Bain for sta694
Russell et al. Exercise and oligomenorrhea
tistical analysis, and Heleen Becker and Sandra Milline for manuscript preparation. We appreciate receiving antibodies against 2-hydroxyestrone-6-carboxymethyloxime-bovine serum albumin provided by Dr. S. C. Chattoraj, Boston University School of Medicine. REFERENCES 1. Dale E, Gerdach DH, Wilhite AL: Menstrual dysfunction in distance runners. Obstet Gynecol 54:47, 1979 2. Baker ER: Menstrual dysfunction and hormonal status in athletic women: a review. Fertil Steril 36:691, 1981 3. Baker ER, Mathur -RS, Kirk RF, Williamson HO: Female runners and secondary amenorrhea: correlation with age, parity, mileage, and plasma hormonal and sex-hormonebinding globulin concentrations. Fertil Steril 36:183, 1981 4. Warren MP: The effects of exercise on pubertal progression and reproductive function in girls. J Clin Endocrinol Metab 51:1150, 1980 5. Frisch RE, Gotz-Welbergen AV, McArthur JW, Albright T, Witschi J, Bullen B, Birnholz J, Reed RB, Hermann H: Delayed menarche and amenorrhea of college athletes in relation to age of onset of training. JAMA 246:1559, 1981 6. Speroff L: Impact of exercise on menstruation and reproduction. Contemp Obstet Gynecol 19:54, 1982 7. Dimsdale JE, Moss J: Plasma catecholamines in stress and exercise. JAMA 243:340, 1980 8. Carr DB, Bullen BA, Skrinar GS: Physical conditioning facilitates the exercise-induced secretion of ~-endorphin and ~-lipoprotein in women. N Engl J Med 305:560, 1981 9. Russell JB, Mitchell DE, Musey PI, Collins DC: The relationship of exercise to anovulatory cycles in female athletes: hormonal and physical characteristics. Obstet Gynecol 63:452, 1984 10. Adashi EY, Rakoff J, Divers W, FishmanJ, Yen SSC: The effect of quickly administered 2-hydroxyestrone on the release of gonadotropins and prolactin before and after estrogen priming in hypogonadal women. Obstet Gynecol 55:363, 1980 11. Pohl CR, Knobil E: The role ofthe central nervous system in the control of ovarian function in higher primates. Annu Rev Physiol 44:583, 1982 12. Reid RL, Hoff J, Yen SSC, Li CH: Effects of exogenous ~-endorphin on pituitary hormone secretion and its disappearance rate in normal human subjects. J Clin Endocrinol Metab 52:1179, 1981 13. Wright K, Collins DC, Preedy JRK: The use of specific radioimmunoassays to determine the renal clearance rates of estrone and 17~-estradiol during the menstrual cycle. J Clin Endocrinol Metab 47:1084, 1978 14. Chattoraj SC, Fanons AS, Cecchini D, Lowe EW: A radioimmunoassay method for urinary catechol estrogens. Steroids 31:375, 1978 15. Sloan AW, Weir JB: Nomograms for prediction of body density and total body fat from skinfold measurements. J Appl Physiol 28:221, 1970 16. McArthur JW, Bullen BA, Beitins IZ, Pagano M, Badger TM, Klibanski A: Hypothalamic amenorrhea in runners of normal body composition. Endocr Res Commun 7:13, 1980 17. Frisch RE, McArthur JW: Menstrual cycles: fatness as a determinant of minimum weight for height necessary for their maintenance or onset. Science 185:949, 1974 Fertility and Sterility
18. Ball P, Emons G, Haupt 0, Hoppen H-O, Knuppen R: Radioimmunoassay of 2-hydroxyestrone. Steroids 31:249, 1978 19. Yoshizawa I, Fishman J: Radioimmunoassay of 2-hydroxyestrone in human plasma. J Clin Endocrinol Metab 32:3,1971 20. Ball P, Knuppen R, Haupt M, Breuer H: Interactions between estrogens and catechol amines. III. Studies on the methylation of catechol estrogens, catechol amines and other catechols by the catechol-O-methyltransferase of human liver. J Clin Endocrinol Metab 34:736, 1972
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21. Yen SSC: Studies of the role of dopamine in the control of prolactin and gonadotropin secretion in humans. In Central Regulation of the Endocrine System, Edited by K Fuxe, T Hokfelt, R Luft. New York, Plenum Press, 1979, p 387 22. Barraclough CA, Sawyer CH: Inhibitions of the release of pituitary ovulatory hormone in the rat by morphine. Endocrinology 57:329, 1955 23. Kalra SP, Simpkins JW: Evidence for noradrenergic mediation of opioid effects on luteinizing hormone secretion. Endocrinology 109:776, 1981 .
Russell et al. Exercise and oligomenorrhea
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FERTILITY AND STERILITY Copyright < 1984 The American Fertility Society
The role of ~-endorphins and catechol estrogens on the hypothalamic-pituitary axis in female athletes*
Jeffrey B. Russell, M.D.t Dorothy E. Mitchell, M.D. t Paull. Musey, Ph.D.:j: Delwood C. Collins, Ph.D.:j:§ Emory University School of Medicine, Veterans Administration Medical Center, Atlanta, Georgia
Competitive swimmers were followed over a 2 -year period when they trained at different levels of exercise which coincided with distinct changes in their menstrual history. Oligomenorrhea was identified in 5 of 13 of these athletes when they swam approximately 100,000 yards per week. Weight and percentage of body fat were not significantly different between the period of oligomenorrhea and regular menstrual function (P = 0.24). Mean and median levels of luteinizing hormone, folliclestimulating hormone, prolactin, and 17f3-estradiol were decreased and catechol estrogens and J3-endorphins were increased in serum during the strenuous, when compared with the moderate, training period. The serum levels of the steroid and protein hormones were similar to those of normal cycling, nonexercising control subjects during moderate exercise (60,000 yards per week). The significant differences between J3-endorphins and catechol estrogens during periods of strenuous exercise suggest an explanation lor oligomenorrhea in female athletes. These hormonal changes result in hypothalamic anovulation, which appears to be reversible, because the hormone levels and menstrual cycles return to normal when the exercise is reduced. Fertil Steril 42:690, 1984
Numerous studies have been initiated to investigate the relationship between physical activity and menstrual dysfunction. 1-8 The etiology of this menstrual dysfunction is not completely understood. Delayed menarche, luteal phase defects, and decreased levels of luteinizing hormone (LH), Received May 14, 1984; revised and accepted July 25, 1984. *Supported in part by the National Institutes of Health grant NIH-1-R01-AG-02012 and Veterans Administration Project 7176-001. tDepartment of Gynecology and Obstetrics. tDepartment of Medicine. §Reprint requests: Delwood C. Collins, Ph.D., Medical Research Service, VA Medical Center, 1670 Clairmont Road, Decatur; Georgia 30033. 690
Russell et al. Exercise and oligomenorrhea
follicle-stimulating hormone (FSH), prolactin (PRL), 1713-estradiol (E 2 ), and progesterone have been confirmed in marathon runners and ballet dancers. Previous clinical studies have implicated rapid weight loss, decreased percentage of body fat, prior menstrual dysfunction, stress, age at onset of training, and amount of training as key factors. Strenuous exercise on a regular basis has been shown to increase l3-endorphins (I3-EP),8 catecholamines,7 and catechol estrogens9 in women. Individually, catechol estrogens have been shown to decrease the basal levels ofLH. lO Catecholamines have been implicated in the regulation of gonadotropin-releasing hormone (GnRH) release from Fertility and Sterility
the median eminence of the hypothalamus. 11 The role of [3-EP in LH release has been investigated in normal subjects. 12 All of these studies implicate [3-EP as responsible for a significant decline in the concentration of LH. The purpose of this study was to determine the relationship between menstrual dysfunction and basal levels of several hormones in the same women during different levels of exercise. These differences were correlated with changes in the menstrual cycle history and give new information about the effect of different levels of exercise on menstrual dysfunction in female athletes.
MATERIALS AND METHODS
Thirteen swimmers from the Dynamo Swim Club of Atlanta, Georgia, were studied during the peak of their training in December 1981 through January 1982 and again from December 1982 through January 1983. The training period in December 1981 (strenuous) consisted of a gradual increase in physical activity until the athletes were swimming 100,000 yards per week. Five swimmers became oligomenorrheic during this period. This peak level of training was followed by a reduction in training to 30,000 yards per week by March 1982. Normal menstrual function returned during this period. Between September 1982 and April 1983, these five swimmers increased their exercise level to 60,000 yards per week in January 1983 and continued to show normal menstrual cycles. The intensity of the training sessions can be defined as swimming 16,000 yards (100,000 yards per week) or 10,000 yards (60,000 yards per week) in a 6-hour period. Thus, the menstrual history and normal pattern of five swimmers were assessed and compared during different levels of exercise. The five swimmers served as their own controls. Six women who did not participate in any organized physical activity, who had a history of normal menstrual cycles, were also used as controls. All participants completed a questionnaire pertaining to age, menarche, menstrual history, parity, height, weight, and oral contraceptive history. Athletes with a history of irregular menses or prior menstrual dysfunction were excluded from the study. Menstrual history was recorded from May 1981 to April 1983. Oligomenorrhea was defined as 60 days or more without a menstrual period" after a minimum of 3 months of Vol. 42, No.5, November 1984
regular cycles. Regular cycles were defined as menses every 27 to 34 days. The swimmers recorded weekly weights along with a log of their exercise. Serum samples were taken from the control subjects between days 13 and 17 of their menstrual cycle. Serum samples were taken from the athletes 30 minutes prior to exercise during both training periods. Serum samples were analyzed for FSH, LH, PRL, E 2, and catechol estrogens by procedures established in this laboratory.13 FSH and LH were measured by radioimmunoassay (RIA) using kits obtained from Radioimmunoassay Systems Laboratories, Carson City, CA. The intraassay coefficients of variation for LH, FSH, and PRL were between 6.8% and 10.2%. The interassay coefficients of variation for these assays varied between 8.1% and 12.8%. [3-EP immunoreactivity and PRL were measured using RIA kits from Immunonuclear Corporation, Stillwater, MN. This is a measure of [3-EP immunoreactivity because the [3-lipotropins have some affinity (= 20%) for this antiserum, and [3-lipotropin fractions cannot be excluded. The intraassay and interassay coefficients of variation for [3-EP were 7.5% and 13.5%, respectively. E2 was measured by RIA with standard procedures developed in this laboratory.13 This antiserum is specific for E2 and shows no significant cross-reaction for other estrogens. Catechol estrogens were determined by RIA using specific antibodies developed against 2-hydroxyestrone-6carboxymethyl oxime as previously described. 14 This antibody cross-reacts almost 100% with 2hydroxyestradiol. Thus, the values measured here reflect catechol estrogen levels. The intraassay and interassay coefficients of variation were 3.8% and 4.6%, respectively, for the catechol estrogens, and 4.9% and 6.3%, respectively, for E 2. The percentage of body fat was determined for each subject. This was obtained from the skinfold thickness measurement using constant-tension Lange skinfold calipers at two sites. One measurement was obtained from the area slightly oblique just above the hipbone in the midaxillary line, and the second from the back of the arm at the midpoint between the acromion and the olecranon processes. The triceps and suprailiac measurements were used to calculate the body density with a standard error of estimation for the equation being ± 0.0082 gm/ml. The percentage of body fat was calculated with the nomogram described by Sloan and Weir.15 Russell et al. Exercise and oligomenorrhea
691
Table 1. Statistical Summary (Mean ± SD with Range in Parentheses) and Analysis ofPhysical Characteristics for the Swimmers During Periods of Moderate and Strenuous Exercise and the N onexercising Control Subjects Swimmers Physical characteristics Age (yr) Weight (kg) Height (in) Menarche ('" 12/;;. 13) % Body fat
Cycle dayc
Control subjects 19.0 ± 1.7 (18--22) 50.6 ± 5.0 (43.1--57.2) 63.0 ± 2.4 (60-66) 5/1 (11-13) 18.8 ± 1.8 (16.2-21.3) 14 (13--18)
Moderate (60,000 yards)
51.8 ± 2.3 (49.4--55.3) 64.2 ± 1.6 (62-66) 17.9 ± 1.7 (15.5-19.6) 15 (3-25)
Strenuous (100,000 yards) 14.4 ± 2.0 (13-17) 48.5 ± 2.1 (46.3--51.3) 63.4 ± 1.8 (61-65) 114 (12-15) 17.4 ± 2.1 (14.6-20.0) 105 (66-116)
Group comparison C vs. 60
C vs. 100a
100 vs. 60b
P = 0.009
P = 0.002
P = 0.66
P = 0.66
P = 0.004
P = 0.36
P = 0.76
P = 0.016
P = 0.42
P = 0.26
P = 0.24
P = 0.054
P = 0.004
P«
0.10
aTwo independent group t-test, Mann-Whitney U-test, or Fisher's exact test. bpaired t-test or Wilcoxon signed rank test. cSample median with range in parentheses.
RESULTS Five competitive swimmers and six control subjects recorded menstrual logs between May 1981 and April 1983. The five swimmers studied had oligomenorrhea for at least 64 to 116 days prior to the time serum samples were taken for steroid and protein analyses. The median cycle dates for collection of blood samples for hormone analysis are shown in Table 1. The mean value (± standard deviation [SD]) for the physical characteristics of the participants are shown in Table 1: All participants were between 13 and 22 years of age. The mean age (± SD) of the swimmers during the period of strenuous exercise was 14.4 ± 2.0 years (range, 13 to 17). The mean age of the control group was significantly higher (19.0 ± 1.7; range, 18 to 22 years; P« 0.01). The mean age of menarche (± SD) in the athletes was 13.5 ± 1.0 years (range, 12 to 15) and was not significantly different from that of the control group (11.8 ± 0.7 years; range, 11 to 13). However, five of six control subjects showed menarche by age 13, compared with only one of five swimmers. The mean body weight (± SD) of the swimmers was 48.5 ± 2.1 kg (range, 46.3 to 51.3) in 1982, during the period of strenuous exercise, and 51.8 ± 2.3 kg (range, 49.4 to 55.3) in 1983, during the period of moderate exercise. The mean weight (± SD) for the control group was 50.6 ± 5.0 kg (range, 43.1 to 57.2). The mean percentage of body fat (± SD) for the swimmers during the period of strenuous exercise (17.4 ± 2.1) was not significantly different from that in 692
Russell et al. Exercise and oligomenorrhea
the moderate exercise period (17.9 ± 1.7). Furthermore, the mean percentage of body fat in the control group was not significantly different from that of the swimmers in either time period (P = 0.42; P = 0.26). The mean and median levels of protein hormones were determined in the swimmers at the two different levels of exercise (Table 2). The median serum LH value for the swimmers during the period of strenuous exercise was significantly lower (11.3 mIUlml) than that for the same individuals during moderate exercise (22.2) (P = 0.02). The median LH value during the period of moderate exercise was not significantly different from that in the control group (21.4; P = 0.66). A similar pattern was seen when the mean LH values were compared. The median level of FSH was significantly lower in swimmers during the period of strenuous exercise (6.8 mIU/ml) when compared with the moderate exercise period (18.2; P « 0.001). The median level ofFSH in the control group (9.6) was intermediate between and significantly different from those in the swimmers during the two periods of exercise. A similar pattern was seen when the mean values were compared. The median serum level for PRL was suppressed to 1.0 ng/ml in the swimmers during strenuous exercise. This was significantly lower than the level during moderate exercise (P = 0.006) as well as that in the control subjects (P = 0.004). The median level of PRL during the moderate exercise period was not significantly differFertility and Sterility
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Table 2. Statistical Summary (Mean [Median) ± SD with Range in Parentheses} and Analysis of Protein Hormones for the
Swimmers During Periods of Moderate and Strenuous Exercise and the Nonexercising Control Subjects Swimmers Hormone
Control subjects
Moderate
No.
(100,000 yards)
6 5 23.1 [21.4] ± 10.5 22.9 [22.2] ± 5.7 m!) (12.3-43.3) (15.9-30.7) 10.9 [9.6] ± 3.5 20.2 [18.2] ± 5.1 FSH (mIU/ m!) (7.1-15.7) (15.3-27.7) PRL (ng/m!) 20.8 [13.5] ± 15.0 10.6 [10.5] ± 3.6 (9.0-47.2) (5.9-16.1)
LH (mIU/
Group comparison (median values)
Strenuous
(60,000 yards)
5 10.9 [11.3] ± 2.8 (7.4-13.6) 6.54 [6.8] ± 2.1 (4.0-9.5) 1.36 [1.0] ± 0.9 (0.7-3.0)
ent from that in the control group (P = 0.18). A similar pattern was seen when the mean values were compared. The mean and median levels of E2 and catechol estrogens are shown in Table 3. The median E2 level during the period of strenuous exercise (52 pg/mD was not significantly different from that during moderate exercise (65 pg/ml) (P = 0.68). The median levels for the swimmers during both periods of exercise were significantly lower than in the control subjects. A similar pattern was seen when the mean values for E2 were compared. The median levels of catechol estrogens were similar for the control group and the swimmers during moderate exercise (median, 35 and 28; P = 0.08). During strenuous exercise, the swimmers had significantly higher levels of catechol estrogens (median, 88; P < < 0.001). A similar pattern was seen when mean levels of catechol estrogens were compared. The median levels of I3-EP immunoreactivity (Table 3) were also significantly higher in the swimmers during their strenuous exercise period when compared with moderate exercise or the control values. The median control value was not significantly different from that of the swimmers during moderate exercise.
C vs. 60
C vs. 100
100 vs. 60
P
=
0.66
P
=
0.02
P
P
=
0.05
P
=
0.04
P «
0.001
P
=
0.18
P
=
0.004
P
0.006
=
0.02
=
DISCUSSION
Oligomenorrhea with or without changes in body fat is well documented in athletes. 16 Our results suggest that oligomenorrhea can occur without a change in the percentage of body fat in swimmers and do not support results from other laboratories which suggest a critical percentage of body fat for the onset and mairitenance of menses. 17 Thus, the clinical recommendation commonly made to these athletes to gain weight may not resolve their oligomenorrhea. Our data suggest that the level or intensity of exercise may be more critical in the transient cessation of menstrual function. The endogenous levels of catechol estrogens were elevated in the swimmers during the period coinciding with strenuous exercise. The values for catechol estrogens in the swimmers on moderate exercise and in the control subjects were similar to those previously reported. 18, 19 This is the first time that a correlation has been made between increased levels of catechol estrogens and oligomenorrhea in the same individuals. Because each subject at the moderate exercise level with normal menstrual cycles serves as her own control, the importance of the control group is greatly
Table 3. Statistical Summary (Mean [Median) ± SD with Range in Parentheses} and Analysis off3-EP Immunoreactivity, E 2 , and
Catechol Estrogens for Swimmers During Periods of Moderate and Strenuous Exercise and the Nonexercising Control Subjects Control subjects
Hormone No. E2 (pg/ml) Catechol estrogens (pg/ml) f3-EP immunoreactivity (pmol/!)
Swimmers Moderate
(60,000 yards)
6 5 264 [193] ± 253 61.8 [65] ± 16.8 (78-759) (36-79) 35.3 [35] ± 7.5 28.0 [28] ± 1.2 (25-46) (26-29) 8.50 [2] ± 15.4 4.40 [4] ± 2.2 (2-40) (2-8)
Vol. 42, No.5, November 1984
Group comparisons
Strenuous (100,000 yards) 5 76.8 [52] ± 61.9 (36-185) 92.4 [88] ± 12.8 (83-115) 31.2 [24] ± 14.3 (18-52)
C vs. 60
C vs. 100
P
=
0.009
P
P
=
0.08
P «
P
=
0.25
P
=
=
0.003 0.001 0.03
100 vs. 60
P
=
0.68
P« P
=
0.001 0.01
Russell et a1. Exercise and oligomenorrhea
693
reduced. Recent studies of the physiologic role of catechol estrogens indicate that they may reduce the rate of degradation of catecholamines by catechol-O-methyltransferase (COMT), thus increasing the availability of catecholamines for biologic action in the hypothalamus. 2o The competition with catechol estrogens for COMT, along with the elevation of catecholamines during exercise, may lead to the suppression of GnRH and PRL by dopamine. 21 The first evidence for an effect of [3-EP on gonadotropin release was shown by Barraclough and Sawyer, 22 who reported that ovulation was blocked by an analog of [3-EP, morphine sulfate, in rats. Kalra and Simpkins23 showed that [3-EP binds to hypothalamic cells which secrete GnRH and blocks GnRH rel-ease by norepinephrine. Our results suggest that [3-EP levels were significantly higher in the swimmers during periods of strenuous exercise when compared with moderate exercise. This is the first time that [3-EP have been measured and shown to be correlated with distinct changes associated with exercise and oligomenorrhea in the same individuals. It should be noted, however, that the [3-EP assay used in this study measures immunoreactivity. Thus, cross-reaction with [3-lipotropin fractions cannot be excluded. The significant differences between catechol estrogens and [3-EP during periods of moderate or strenuous exercise suggest an explanation for oligomenorrhea in female athletes. Increased levels of [3-EP, catechol estrogens, and dopamine during strenuous exercise may interact to cause suppression of GnRH release, either directly or indirectly. Our results suggest that the elevated catechol estrogens may compete with catecholamines for COMT, leading to decreased degradation of dopamine and increased inhibitory effect of dopamine on GnRH. The decreased basal levels of PRL seen in swimmers during strenuous exercise may reflect this elevated dopamine level. Furthermore, the stimulatory effect of norepinephrine on GnRH may be inhibited by the increased level of [3-EP which bind to norepinephrine receptors in the hypothalamus, leading to a suppression of LH and FSH. These hormonal changes result in hypothalamic anovulation which appears to be reversible, because the hormone levels return to normal when the level of exercise is reduced. Acknowledgments. We thank Mr. Pat Hogan, Coach, and members of the Atlanta Dynamo Club, Dr. Ray Bain for sta694
Russell et al. Exercise and oligomenorrhea
tistical analysis, and Heleen Becker and Sandra Milline for manuscript preparation. We appreciate receiving antibodies against 2-hydroxyestrone-6-carboxymethyloxime-bovine serum albumin provided by Dr. S. C. Chattoraj, Boston University School of Medicine. REFERENCES 1. Dale E, Gerdach DH, Wilhite AL: Menstrual dysfunction in distance runners. Obstet Gynecol 54:47, 1979 2. Baker ER: Menstrual dysfunction and hormonal status in athletic women: a review. Fertil Steril 36:691, 1981 3. Baker ER, Mathur -RS, Kirk RF, Williamson HO: Female runners and secondary amenorrhea: correlation with age, parity, mileage, and plasma hormonal and sex-hormonebinding globulin concentrations. Fertil Steril 36:183, 1981 4. Warren MP: The effects of exercise on pubertal progression and reproductive function in girls. J Clin Endocrinol Metab 51:1150, 1980 5. Frisch RE, Gotz-Welbergen AV, McArthur JW, Albright T, Witschi J, Bullen B, Birnholz J, Reed RB, Hermann H: Delayed menarche and amenorrhea of college athletes in relation to age of onset of training. JAMA 246:1559, 1981 6. Speroff L: Impact of exercise on menstruation and reproduction. Contemp Obstet Gynecol 19:54, 1982 7. Dimsdale JE, Moss J: Plasma catecholamines in stress and exercise. JAMA 243:340, 1980 8. Carr DB, Bullen BA, Skrinar GS: Physical conditioning facilitates the exercise-induced secretion of ~-endorphin and ~-lipoprotein in women. N Engl J Med 305:560, 1981 9. Russell JB, Mitchell DE, Musey PI, Collins DC: The relationship of exercise to anovulatory cycles in female athletes: hormonal and physical characteristics. Obstet Gynecol 63:452, 1984 10. Adashi EY, Rakoff J, Divers W, FishmanJ, Yen SSC: The effect of quickly administered 2-hydroxyestrone on the release of gonadotropins and prolactin before and after estrogen priming in hypogonadal women. Obstet Gynecol 55:363, 1980 11. Pohl CR, Knobil E: The role ofthe central nervous system in the control of ovarian function in higher primates. Annu Rev Physiol 44:583, 1982 12. Reid RL, Hoff J, Yen SSC, Li CH: Effects of exogenous ~-endorphin on pituitary hormone secretion and its disappearance rate in normal human subjects. J Clin Endocrinol Metab 52:1179, 1981 13. Wright K, Collins DC, Preedy JRK: The use of specific radioimmunoassays to determine the renal clearance rates of estrone and 17~-estradiol during the menstrual cycle. J Clin Endocrinol Metab 47:1084, 1978 14. Chattoraj SC, Fanons AS, Cecchini D, Lowe EW: A radioimmunoassay method for urinary catechol estrogens. Steroids 31:375, 1978 15. Sloan AW, Weir JB: Nomograms for prediction of body density and total body fat from skinfold measurements. J Appl Physiol 28:221, 1970 16. McArthur JW, Bullen BA, Beitins IZ, Pagano M, Badger TM, Klibanski A: Hypothalamic amenorrhea in runners of normal body composition. Endocr Res Commun 7:13, 1980 17. Frisch RE, McArthur JW: Menstrual cycles: fatness as a determinant of minimum weight for height necessary for their maintenance or onset. Science 185:949, 1974 Fertility and Sterility
18. Ball P, Emons G, Haupt 0, Hoppen H-O, Knuppen R: Radioimmunoassay of 2-hydroxyestrone. Steroids 31:249, 1978 19. Yoshizawa I, Fishman J: Radioimmunoassay of 2-hydroxyestrone in human plasma. J Clin Endocrinol Metab 32:3,1971 20. Ball P, Knuppen R, Haupt M, Breuer H: Interactions between estrogens and catechol amines. III. Studies on the methylation of catechol estrogens, catechol amines and other catechols by the catechol-O-methyltransferase of human liver. J Clin Endocrinol Metab 34:736, 1972
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21. Yen SSC: Studies of the role of dopamine in the control of prolactin and gonadotropin secretion in humans. In Central Regulation of the Endocrine System, Edited by K Fuxe, T Hokfelt, R Luft. New York, Plenum Press, 1979, p 387 22. Barraclough CA, Sawyer CH: Inhibitions of the release of pituitary ovulatory hormone in the rat by morphine. Endocrinology 57:329, 1955 23. Kalra SP, Simpkins JW: Evidence for noradrenergic mediation of opioid effects on luteinizing hormone secretion. Endocrinology 109:776, 1981 .
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