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Implications of growth hormone release in sleep
Implications By
of Growth Hormone
Release in Sleep
W. P. VANDERLAAN, D. C. PARKER,L. G. ROSSMAN AND E. F. VANDERLAAN
Growth hormone (HGH) in plasma of volunteers at rest was in barely detectable concentration during the day except for minor post prandial rises. Early in sleep a major rise occurred and this was related to the first cycle of sleep and to stages III and IV by EEG criteria. Glucose infusion nearly doubling the blood sugar failed to suppress HGH release. In anorexia nervosa glucose loading stimulated
HGH release in eight of ten awake subjects, contrasting with unresponsiveness of obese subjects to stimuli of HGH release. We conclude that sleep release of HGH under CNS influence is of major importance and suggest that the brain monitors the nutritional state and regulates HGH release according to need. (Metabolism 19: No. 10, October, 891897, 1970)
W
E ARE HONORED TO BE PARTICIPANTS in the celebration of Dr. Astwood’s 60th birthday. Such occasions stimulate stock-taking and we wish to present some thoughts on the contra lof the release of growth hormone by the pituitary gland. Both Astwood and Cassidy’s and also Williams’s recent books on endocrinology state that growth hormone (HGH) secretion, as judged by radioimmunoassay of plasma, is stimulated by hypoglycemia and suppressed by hyperglycemia.lJ Hypoglycemia must be induced rapidly and the fall is generally an adequate stimulus for testing purposes if the blood sugar reaches 50 per cent of fasting or less in not more than 30 minutes after insulin has been administered. On the other hand, failure of hyperglycemia to suppress HGH secretion is considered major evidence for the diagnosis of acromegaly. In addition to hypoglycemia, stress, exercise, fasting, and the infusion of amino acids, especially arginine, are recognized as stimuli to the secretion of growth hormone in man. The earlier demonstration by Raben and Hollenberg3 that growth hormone resulted in rises in free fatty acid concentrations in plasma, coupled with the observation that hypoglycemia was a potent stimulus to growth hormone release, led to the attractive hypothesis that growth hormone was a minute-to-minute regulator of substrate availability. The thrust of this presentation is that the central nervous system monitors the secretion of HGH and that its activation of the pituitary gland to secrete HGH during sleep is of major physiologic importance. The adaptive responses of this activating system appear to include From the Endocrine Division, Scripps Clinic and Research Foundation, La Jolla, Calif. Supported by USPHS Grants AM-1328 and AM-5249 and by grants from the McCarthy Foundation and the Diabetes Association of Southern California. W. P. VANDERLAAN, M.D.: Head, Endocrine Division, Scripps Clinic and Research Division, Scripps Foundation, La Jolla, Calif. D. C. PARKER,M.D.: Associate, Endocrine Clinic and Research Foundation, La Jolla, Calif. L. G. ROSSMAN,B.S.: Research Assistant, Endocrine Division, Scripps Clinic and Research Foundation, La Jolla, Calif. E. F. VANDERLAAN, B.A.: Research Assistant, Endocrine Division, Scripps Clinic and Research Foundation, La Jolla, Calif. METABOLISM,VOL. 19, No. 10 (OCTOBER), 1970
891
892
VANDER LAAN ET AL.
such a complete range that in states of overnutrition there is an attenuated response to all stimuli to HGH release, whereas in malnutrition even glucose administration appears to act as a stimulus. If this thesis is found correct by future observations, it will appear that the CNS somehow monitors the nutritional state of the organism. MATERIALS AND METHODS
Sixteen lean, healthy, young male volunteers comprised the initial study group. Via intracaths placed in antecubital veins they were bled hourly during a single 24-hour period while they remained at bed rest but held to a normal schedule of meals. Sleep was not disturbed by the procedure. When these studies revealed marked nychthemeral variations with increased concentrations of plasma HGH during sleep, arrangements were made for eledroencephalographic monitoring of sleep in additional volunteers. The earlier studies were made in cooperation with Drs. Jon Sassin and Laveme Johnson of the United States Navy Medical Neuropsychiatric Unit, San Diego, California, and subsequently they were made in our own sleep laboratory. Polygraphic recordings and scoring of sleep were done by standard techniques as previously noted.’ Sleep was analyzed by cycles which terminated with REM stages and which were classified by the lowest stage of sleep reached. Stage 2 was considered non-slow wave (NSW) and Stages 3 and 4, slow wave (SW). To study the effects of hyperglycemia during sleep, two subjects were infused into the right antecubital veins with a solution of glucose at a rate of 6 mg./kg. body weight/ minute. This was done in the early minutes of sleep on the third of three consecutive nights spent in our laboratory for the study of sleep. This laboratory consists of an area of 300 square feet partitioned so that the patient sleeps in an air conditioned, darkened and soundproof room. The electroencephalographic conduit from the console at the head of the bed and a length of fine plastic tubing are led through a channel in the wall to the main portion of the laboratory. The volume of the tubing is filled with lightly heparinized saline. Samples of blood were taken from the left arm every 15 to 30 minutes during the entire period of sleep and these wre analyzd for glucose, immunoreactive insulin (IRI), and HGH. In the radioimmunoassays, separation of the “bound and free” fractions was done with the charcoal-dextran method of Herbert.5 Wilhelmi HGH standard HS612B was a gift of the National Pituitary Agency. RESULTS
Clinical Studies Nychthemeral Variations. This study showed a marked rise during 14 of 16 subjects, the peak HGH concentration reaching average values ng./ml. & 2.6 (SEM). The peaks were noted to occur predominantly early hours of behaviorally adjudged sleep. The sleeping peaks of hormone release were greater than the postcibal rises (8.3 ng./ml.
sleep in
of 17.2 in the growth
t 0.8) and these latter rises were noted only in seven subjects. Otherwise plasma HGH concentrations were below 2 ng./ml. In only two subjects was there a waking HGH response in excess of that individual’s peak release in sleep. This release of HGH during sleep confirmed similar observations of Quabbe et a1.6 We call particular attention to the fact that in these individuals, well-adjusted to hospital procedures, plasma HGH concentrations remained at the edge of detectability except for minor rises after meals. The major rise occurred as a single peak in early sleep. Infusion
of Glucose
During
Sleep.
Two
subjects
were
studied
for
three
GROWTH
HORMONE
RELEASE
Table
l.-HGH
Night 1
22.1 (88) 23.6 (76)
Subject 1 Subject 2
893
IN SLEEP
Peak During
Sleep*
Time
Night 2
Time
Night 3
Time
100 90
21.2 (114) 23.6 (70)
96 73
20.7 (180) 23.2 (370)
106 74
* The maximum observed plasma HGH, ng./ml., the blood glucose, milligrams per cent, in parentheses, and the time in minutes after electroencephalographic onset of sleep are presented for three nights. The third night glucose was infused from the onset of sleep.
consecutive nights each. The first two nights were intended to set the pattern for the sleep release of growth hormone and the third night to test for possible alteration of that pattern resulting from induction of hyperglycemia. During the two base line nights IRI and glucose concentrations were remarkably stable. On the night of glucose infusion each subject showed a release of growth hormone nearly identical to that of the control nights. The release of HGH was not altered by hyperglycemia in terms of time after the onset of sleep or the shape or height of the curve plotted to show rise and fall. These data, in respect to peak values of HGH according to time after onset of sleep, are shown in Table 1 and are shown graphically for one subject in Fig. 1. Thus glucose infusion, which maintained a constant elevation of plasma glucose of 188 per cent of mean basal value (91 to 172 mg./ 100 ml.) caused no suppression of HGH in one subject, and an even greater rise in glucose concentration was equally ineffective in the second. Thus the data suggest that the central nervous system activates the pituitary gland during sleep and that the central nervous system is not suppressed in this activation by hyperglycemia. The sleep release of growth hormone is similar to stress in this respect: it is well accepted and notable that the growth hormone release induced by the infusion of arginine occurs despite a rise in blood sugar. Studies of Adaptation in HGH Release. One approach to the study of hormonal controls is to look for adaptive mechanisms. Obesity appeared to us to induce an adaptive suppression of the magnitude of release of growth 25 O____-__ 20-
NIGHTS
1.2
CONTROL
0,.
NIGHT
3
GLUCOSE
V
(O-200
MIN.)
:
HGH: “p/ml.
IS -
: \
!
IO -
;
:
ihf
I-
O0
MINUTES
Fig. 1 .-Constant
glucose
infusion;
300
200
100
AFTER
failure
SLEEP
400
ONSET
to inhibit
sleep release
of HGH.
894
VANDER
LAAN
ET AL.
hormone in the arginine stimulation test. Norms were established for the HGH response to arginine infusion using a dosage of 0.5 Gm./Kg. body weight/30 minutes and the data (Table 2) are presented for men, women, boys and girls. Since the differences between women and children were not statistically significant these groups were combined. Eight of 13 obese women showed impaired responses and the mean peak for the entire group of obese women, 6.7 * 1.0 ng./ml. was significantly different from the normal women (p < 0.00001 by Student’s t test). Three of the impaired responses occurred in women more than 100 per cent above ideal weight, two in the group of four with impaired glucose tolerance, and four in the group of six who were menopausal. Impairment of HGH release to the stimulus of arginine infusion could only be correlated to the obesity. The recent data of London0 et al.? showing that progressive weight loss in the obese was associated with a corresponding increase in the peak of growth hormone release to a standard stimulus provided conclusive evidence that obesity results in reversible changes which presumably are adaptive. Our experience with obese patients studied in sleep for release of growth hormone indicates impairment but we have not yet had opportunity to study obese patients before and after weight loss. The suppression of growth hormone release in the obese suggested that the malnourished might profitably be studied. Elevations of growth hormone concentration in plasma have been noted in anorexia nervosa by Glick et al.” In the discussion period of Glick’s presentation, Dr. M. M. Grumbach confirmed this and the late Dr. Jane Russell summarized her view about the importance of growth hormone in the regulation of nitrogen balance in the fasting state. In the fasted hypophysectomized rat failure to conserve nitrogen occurs, unlike the success of the intact animal. She noted that the most marked influence of the pituitary was found when hypophysectomized and sham-operated rats were fed a diet containing small but adequate amounts of protein in an otherwise balanced diet. In the hypophysectomized nitrogen excretion was treble that of the sham-operated rat indicating that the pituitary gland and presumably growth hormone were necessary for protein anabolism particularly when protein intake was barely sufficient. In children with kwashiorkor Pimstone et al.” observed elevations of plasma growth hormone concentrations and with protein repletion he found them to return to normal in one or two weeks. Malnutrition __ ,._..
_.
Table ~~~
2.-Peak
~~~~
Men Women Boys Girls Women, boys and girls combined Obese Women
HGH
Response
Mean -c SiM
8.2 + 1.1 21.2 + 2.3 28.5 r 7.4 18.5 2 2.8
in Arginine
Infusion
Range
3.6 113.5 11 to above 40
Tests* 95% ConfidenceRange
3.1 to 18.2
7.2 to 55.7 23.4 t 2.9 6.7 + 1.0 -______. * The maximum growth hormone concentration in ng./ml. observed after arginine infusion is presented. The 95 per cent confidence range gives data transformed against Poussin skewness.
GROWTH
HORMONE
RELEASE
895
IN SLEEP
would appear to have induced adaptations in pituitary function such that overnutrition on the one hand and undernutrition on the other present an understandable continuum. We also performed standard glucose tolerance tests in 10 patients with anorexia nervosa. Only one showed glucose intolerance and delay in insulin release. Eight of ten showed an early rise in growth hormone concentration (Table 3). We interpret these results as entirely in keeping with Dr. Russell’s viewpoint on fasting. It seems reasonable that in patients with substandard diets and severe weight loss any sudden availability of calories would result in an opportunity for protein synthesis. The release of growth hormone would serve the useful function of facilitating protein synthesis, possibly from amino acids diverted from gluconeogenesis. In our opinion the data in Table 3 suggest the release of growth hormone resulted from glucose loading rather than the stress of the manipulations. In three of the patients plasma was drawn at minus 60 and minus 30 minutes as well as just preceding the administration of glucose. In a fourth the blood was drawn through a venous catheter which was not disturbed through the entire procedure. These tests led to the same conclusion as derived from standard glucose tolerance testing. Studies in Hydrancephaly. It seems highly appropriate to ask how much of the central nervous system must be represented if there is to be CNS activation of the pituitary gland to release growth hormone. Through the cooperation of Profs. William Nyhan and Louis Gluck at the University Hospital of San Diego County, we have begun to explore this question in hydrancephalic infants. The data are preliminary but indicate that there is a constant concentration of growth hormone in blood, not varying with sleep or insulin administration. Arginine did induce a rise in one patient studied. The hydrancephalic infants having no cerebral cortex showed no electroencephalographic waves so that sleep could only be behaviorally adjudged. Hyperglycemia and Thyrotrophin. There is recent evidence that glucose loadTable
Patient
1 2 3 4 5 6 7 8 9 10
3.-Maximum Anorexia
Es% 19.2 5.6 8.6 1.1 3.1 1.2 1.5 9.6 1.0 1.0
Plasma HGH, IRI and Glucose in Ten Patients Nervosa During Oral Glucose Tolerance Tests* Max HGH (w/ml.) 36.5 28.4 26.7 5.0 8.7 6.4 > 40.0 > 40.0 16.5 1.0
(Time) (1) (1) (1) (2) (1) (1) (2) (‘/2) (5) t-j
MaxIRI (I*U/ml.) 255 51 122 33 60 186 17 338 67 108
( Time)
(2) (3) (1) (1) (1) (1) (‘/2) (1) (fi) (1)
With
Max Glucose
(mg./lOO ml.) 184 117 150 123 212 111 142 166 106 133
Time
(2) (1) (1) (S)
WI (1) W) (1) W) (Xl
* Oral glucose tolerance tests were performed using lOO-Gm. glucose load. Time in hours after glucose loading is indicated in parentheses, and in the first eight subjects a relatively early rise in HGH, as estimated from the peak reached, was observed. HGH reached maximum concentration before IRI in six instances.
896
VANDER
LAAN
ET AL.
ing tends not only to suppress growth hormone release but also corticotropin, even in Addison’s disease.lO The response is brief and not to normal concentrations but of very substantial magnitude. We have tried to suppress thyrotrophin in myxedema by glucose administration and observed no response. Postprandial suppression of growth hormone and corticotropin in health would favor the action of insulin, and postprandial bliss rather than stress has long been advised to patients by their physicians. It appears unneccessary for thyrotrophin to be suppressed for the full benefit of relaxation in the postprandial state to be experienced. SUMMARY
The release of growth hormone during sleep appears to be a clear example of the purposeful physiological activation of the endocrine system by the central nervous system. The slow wave activity of the cortex may reflect great activity in the limbic or other system rather than being the initiator. It is not clear that so-called stress activates growth hormone release by a different pathway than does sleep; one can only speak of a central nervous system activation. The studies of sleep reversal make clear that the activation of the pituitary gland is not a function of time but truly a phenomenon of sleep. Our studies relate this release to slow wave sleep and we record here evidence that hyperglycemia does not suppress the sleep release of growth hormone. We have studied anorexia nervosa as for us the most available disorder of malnutrition, and we call to attention the frequency with which glucose loading stimulates an early release of HGH. Although glucose tolerance tests may be called stress, it seems more appropriate in our opinion to note that the growth hormone release in response to hyperglycemia may serve a useful function in the malnourished, and we submit that the release of growth hormone may be stimulated by a highly sophisticated sensor, well aware of the nutritional needs of the body. In this sense the sluggish responses of the obese to stimuli of growth hormone release can be considered the opposite extreme of the response of the malnourished in whom release of growth hormone appears to occur with glucose loading. Although such responses have been called paradoxical they may serve a useful purpose. We feel it will be of interest to know whether release of growth hormone is a general response to glucose loading in the malnourished. If this proves to be the case there exists a relatively simple means of testing for malnutrition. It may be noted that other reports in which glucose loading was noted to stimulate growth hormone releasell-I” included disorders in which protein synthesis probably were impaired, although alternative explanations may have applied. What are the implications of the release of HGH during sleep for disease states? Will there be disease from failure of this mechanism? Does acromegaly represent a constant central nervous system drive to the pituitary or a primary glandular disorder? Did Macbeth fail to enter deep sleep which “no more knits up the ravelled sleave of care ?” Almost all the important questions remain to be answered, and we can only hope to have stimulated an interest in them.
897
GROWTH HORMONE RELEASE IN SLEEP
REFERENCES 1. Frantz, A. G.: Growth hormone in blood. In Astwood, E. B., and Cassidy, C. E. (Eds.): Clinical Endocrinology 2. New York, Grune & Stratton, 1968, p. 40. 2. Daughaday, W.: The adenohypophysis. In Williams, R. H. (Ed.): A Textbook of Endocrinology. Philadelphia, Saunders, 1968, p. 27. 3. Raben, M. S., and Hollenberg, C. H.: Effect of growth hormone in plasma fatty acids. J. Clin. Invest. 38:484, 1959. 4. Parker, D. C., Sassin, J. F., Mace, J. W., Gotlin, R. W., and Rossman, L. G.: Human growth hormone release during sleep: Electroencephalographic recording. J. Clin. Endocr. 29:871, 1969. 5. Herbert, V., Lau, K. S., Gottlieb, C. W., and Bleicher, S. J.: Coated charcoal immunoassay of insulin. J. Clin. Endocr. 25:1375, 1965. 6. Quabbe, H. J., Schilling, E., and Helge, H.: Pattern of growth hormone secretion during a 24 hour fast, J. Clin. Endocr. 26: 1173, 1966. 7. Londono, J. H., Gallaher, T. F., Jr., and Bray, G. A.: Effect of weight reduction, triiodothyronine, and stilbestrol on growth
hormone in obesity. Metabolism 18:986, 1969. 8. Glick, S. J., Roth, J., YaIow, R. S., and Berson, S. A.: The regulation of growth hormone secretion. Rec. Progr. Hormone Res. 21:241, 1965. 9. Pimstone, B. L., Wittmann, W., Hansen, J. D. L., and Murray, P.: Growth hormone and kwashiorkor: Role of protein in homeostasis. Lancet 2:779, 1966. 10. Rayyis, S. S., and Bethune, J. E.: Effect of blood glucose on ACTH secretion in man. Clin. Res. 18: 171, 1970. 11. Samaan, N., Cumming, W. S., Craig, J. W., and Pearson, 0. H.: Serum growth hormone and insulin levels in severe renal disease. Diabetes 15 : 546, 1966. 12. -, Pearson, 0. H., Gonzalez, D., and Llerena, 0.: Paradoxical secretion of growth hormone in patients with breast cancer. J. Lab. Clin. Med. 68:1011, 1966. 13. Perlroth, M. G., Tschudy, D. P., Waxman, A., and Odell, W. D.: Abnormalities of growth hormone regulation in acute intermittent porphyria. Metabolism 16:87, 1967.
of Growth Hormone
Release in Sleep
W. P. VANDERLAAN, D. C. PARKER,L. G. ROSSMAN AND E. F. VANDERLAAN
Growth hormone (HGH) in plasma of volunteers at rest was in barely detectable concentration during the day except for minor post prandial rises. Early in sleep a major rise occurred and this was related to the first cycle of sleep and to stages III and IV by EEG criteria. Glucose infusion nearly doubling the blood sugar failed to suppress HGH release. In anorexia nervosa glucose loading stimulated
HGH release in eight of ten awake subjects, contrasting with unresponsiveness of obese subjects to stimuli of HGH release. We conclude that sleep release of HGH under CNS influence is of major importance and suggest that the brain monitors the nutritional state and regulates HGH release according to need. (Metabolism 19: No. 10, October, 891897, 1970)
W
E ARE HONORED TO BE PARTICIPANTS in the celebration of Dr. Astwood’s 60th birthday. Such occasions stimulate stock-taking and we wish to present some thoughts on the contra lof the release of growth hormone by the pituitary gland. Both Astwood and Cassidy’s and also Williams’s recent books on endocrinology state that growth hormone (HGH) secretion, as judged by radioimmunoassay of plasma, is stimulated by hypoglycemia and suppressed by hyperglycemia.lJ Hypoglycemia must be induced rapidly and the fall is generally an adequate stimulus for testing purposes if the blood sugar reaches 50 per cent of fasting or less in not more than 30 minutes after insulin has been administered. On the other hand, failure of hyperglycemia to suppress HGH secretion is considered major evidence for the diagnosis of acromegaly. In addition to hypoglycemia, stress, exercise, fasting, and the infusion of amino acids, especially arginine, are recognized as stimuli to the secretion of growth hormone in man. The earlier demonstration by Raben and Hollenberg3 that growth hormone resulted in rises in free fatty acid concentrations in plasma, coupled with the observation that hypoglycemia was a potent stimulus to growth hormone release, led to the attractive hypothesis that growth hormone was a minute-to-minute regulator of substrate availability. The thrust of this presentation is that the central nervous system monitors the secretion of HGH and that its activation of the pituitary gland to secrete HGH during sleep is of major physiologic importance. The adaptive responses of this activating system appear to include From the Endocrine Division, Scripps Clinic and Research Foundation, La Jolla, Calif. Supported by USPHS Grants AM-1328 and AM-5249 and by grants from the McCarthy Foundation and the Diabetes Association of Southern California. W. P. VANDERLAAN, M.D.: Head, Endocrine Division, Scripps Clinic and Research Division, Scripps Foundation, La Jolla, Calif. D. C. PARKER,M.D.: Associate, Endocrine Clinic and Research Foundation, La Jolla, Calif. L. G. ROSSMAN,B.S.: Research Assistant, Endocrine Division, Scripps Clinic and Research Foundation, La Jolla, Calif. E. F. VANDERLAAN, B.A.: Research Assistant, Endocrine Division, Scripps Clinic and Research Foundation, La Jolla, Calif. METABOLISM,VOL. 19, No. 10 (OCTOBER), 1970
891
892
VANDER LAAN ET AL.
such a complete range that in states of overnutrition there is an attenuated response to all stimuli to HGH release, whereas in malnutrition even glucose administration appears to act as a stimulus. If this thesis is found correct by future observations, it will appear that the CNS somehow monitors the nutritional state of the organism. MATERIALS AND METHODS
Sixteen lean, healthy, young male volunteers comprised the initial study group. Via intracaths placed in antecubital veins they were bled hourly during a single 24-hour period while they remained at bed rest but held to a normal schedule of meals. Sleep was not disturbed by the procedure. When these studies revealed marked nychthemeral variations with increased concentrations of plasma HGH during sleep, arrangements were made for eledroencephalographic monitoring of sleep in additional volunteers. The earlier studies were made in cooperation with Drs. Jon Sassin and Laveme Johnson of the United States Navy Medical Neuropsychiatric Unit, San Diego, California, and subsequently they were made in our own sleep laboratory. Polygraphic recordings and scoring of sleep were done by standard techniques as previously noted.’ Sleep was analyzed by cycles which terminated with REM stages and which were classified by the lowest stage of sleep reached. Stage 2 was considered non-slow wave (NSW) and Stages 3 and 4, slow wave (SW). To study the effects of hyperglycemia during sleep, two subjects were infused into the right antecubital veins with a solution of glucose at a rate of 6 mg./kg. body weight/ minute. This was done in the early minutes of sleep on the third of three consecutive nights spent in our laboratory for the study of sleep. This laboratory consists of an area of 300 square feet partitioned so that the patient sleeps in an air conditioned, darkened and soundproof room. The electroencephalographic conduit from the console at the head of the bed and a length of fine plastic tubing are led through a channel in the wall to the main portion of the laboratory. The volume of the tubing is filled with lightly heparinized saline. Samples of blood were taken from the left arm every 15 to 30 minutes during the entire period of sleep and these wre analyzd for glucose, immunoreactive insulin (IRI), and HGH. In the radioimmunoassays, separation of the “bound and free” fractions was done with the charcoal-dextran method of Herbert.5 Wilhelmi HGH standard HS612B was a gift of the National Pituitary Agency. RESULTS
Clinical Studies Nychthemeral Variations. This study showed a marked rise during 14 of 16 subjects, the peak HGH concentration reaching average values ng./ml. & 2.6 (SEM). The peaks were noted to occur predominantly early hours of behaviorally adjudged sleep. The sleeping peaks of hormone release were greater than the postcibal rises (8.3 ng./ml.
sleep in
of 17.2 in the growth
t 0.8) and these latter rises were noted only in seven subjects. Otherwise plasma HGH concentrations were below 2 ng./ml. In only two subjects was there a waking HGH response in excess of that individual’s peak release in sleep. This release of HGH during sleep confirmed similar observations of Quabbe et a1.6 We call particular attention to the fact that in these individuals, well-adjusted to hospital procedures, plasma HGH concentrations remained at the edge of detectability except for minor rises after meals. The major rise occurred as a single peak in early sleep. Infusion
of Glucose
During
Sleep.
Two
subjects
were
studied
for
three
GROWTH
HORMONE
RELEASE
Table
l.-HGH
Night 1
22.1 (88) 23.6 (76)
Subject 1 Subject 2
893
IN SLEEP
Peak During
Sleep*
Time
Night 2
Time
Night 3
Time
100 90
21.2 (114) 23.6 (70)
96 73
20.7 (180) 23.2 (370)
106 74
* The maximum observed plasma HGH, ng./ml., the blood glucose, milligrams per cent, in parentheses, and the time in minutes after electroencephalographic onset of sleep are presented for three nights. The third night glucose was infused from the onset of sleep.
consecutive nights each. The first two nights were intended to set the pattern for the sleep release of growth hormone and the third night to test for possible alteration of that pattern resulting from induction of hyperglycemia. During the two base line nights IRI and glucose concentrations were remarkably stable. On the night of glucose infusion each subject showed a release of growth hormone nearly identical to that of the control nights. The release of HGH was not altered by hyperglycemia in terms of time after the onset of sleep or the shape or height of the curve plotted to show rise and fall. These data, in respect to peak values of HGH according to time after onset of sleep, are shown in Table 1 and are shown graphically for one subject in Fig. 1. Thus glucose infusion, which maintained a constant elevation of plasma glucose of 188 per cent of mean basal value (91 to 172 mg./ 100 ml.) caused no suppression of HGH in one subject, and an even greater rise in glucose concentration was equally ineffective in the second. Thus the data suggest that the central nervous system activates the pituitary gland during sleep and that the central nervous system is not suppressed in this activation by hyperglycemia. The sleep release of growth hormone is similar to stress in this respect: it is well accepted and notable that the growth hormone release induced by the infusion of arginine occurs despite a rise in blood sugar. Studies of Adaptation in HGH Release. One approach to the study of hormonal controls is to look for adaptive mechanisms. Obesity appeared to us to induce an adaptive suppression of the magnitude of release of growth 25 O____-__ 20-
NIGHTS
1.2
CONTROL
0,.
NIGHT
3
GLUCOSE
V
(O-200
MIN.)
:
HGH: “p/ml.
IS -
: \
!
IO -
;
:
ihf
I-
O0
MINUTES
Fig. 1 .-Constant
glucose
infusion;
300
200
100
AFTER
failure
SLEEP
400
ONSET
to inhibit
sleep release
of HGH.
894
VANDER
LAAN
ET AL.
hormone in the arginine stimulation test. Norms were established for the HGH response to arginine infusion using a dosage of 0.5 Gm./Kg. body weight/30 minutes and the data (Table 2) are presented for men, women, boys and girls. Since the differences between women and children were not statistically significant these groups were combined. Eight of 13 obese women showed impaired responses and the mean peak for the entire group of obese women, 6.7 * 1.0 ng./ml. was significantly different from the normal women (p < 0.00001 by Student’s t test). Three of the impaired responses occurred in women more than 100 per cent above ideal weight, two in the group of four with impaired glucose tolerance, and four in the group of six who were menopausal. Impairment of HGH release to the stimulus of arginine infusion could only be correlated to the obesity. The recent data of London0 et al.? showing that progressive weight loss in the obese was associated with a corresponding increase in the peak of growth hormone release to a standard stimulus provided conclusive evidence that obesity results in reversible changes which presumably are adaptive. Our experience with obese patients studied in sleep for release of growth hormone indicates impairment but we have not yet had opportunity to study obese patients before and after weight loss. The suppression of growth hormone release in the obese suggested that the malnourished might profitably be studied. Elevations of growth hormone concentration in plasma have been noted in anorexia nervosa by Glick et al.” In the discussion period of Glick’s presentation, Dr. M. M. Grumbach confirmed this and the late Dr. Jane Russell summarized her view about the importance of growth hormone in the regulation of nitrogen balance in the fasting state. In the fasted hypophysectomized rat failure to conserve nitrogen occurs, unlike the success of the intact animal. She noted that the most marked influence of the pituitary was found when hypophysectomized and sham-operated rats were fed a diet containing small but adequate amounts of protein in an otherwise balanced diet. In the hypophysectomized nitrogen excretion was treble that of the sham-operated rat indicating that the pituitary gland and presumably growth hormone were necessary for protein anabolism particularly when protein intake was barely sufficient. In children with kwashiorkor Pimstone et al.” observed elevations of plasma growth hormone concentrations and with protein repletion he found them to return to normal in one or two weeks. Malnutrition __ ,._..
_.
Table ~~~
2.-Peak
~~~~
Men Women Boys Girls Women, boys and girls combined Obese Women
HGH
Response
Mean -c SiM
8.2 + 1.1 21.2 + 2.3 28.5 r 7.4 18.5 2 2.8
in Arginine
Infusion
Range
3.6 113.5 11 to above 40
Tests* 95% ConfidenceRange
3.1 to 18.2
7.2 to 55.7 23.4 t 2.9 6.7 + 1.0 -______. * The maximum growth hormone concentration in ng./ml. observed after arginine infusion is presented. The 95 per cent confidence range gives data transformed against Poussin skewness.
GROWTH
HORMONE
RELEASE
895
IN SLEEP
would appear to have induced adaptations in pituitary function such that overnutrition on the one hand and undernutrition on the other present an understandable continuum. We also performed standard glucose tolerance tests in 10 patients with anorexia nervosa. Only one showed glucose intolerance and delay in insulin release. Eight of ten showed an early rise in growth hormone concentration (Table 3). We interpret these results as entirely in keeping with Dr. Russell’s viewpoint on fasting. It seems reasonable that in patients with substandard diets and severe weight loss any sudden availability of calories would result in an opportunity for protein synthesis. The release of growth hormone would serve the useful function of facilitating protein synthesis, possibly from amino acids diverted from gluconeogenesis. In our opinion the data in Table 3 suggest the release of growth hormone resulted from glucose loading rather than the stress of the manipulations. In three of the patients plasma was drawn at minus 60 and minus 30 minutes as well as just preceding the administration of glucose. In a fourth the blood was drawn through a venous catheter which was not disturbed through the entire procedure. These tests led to the same conclusion as derived from standard glucose tolerance testing. Studies in Hydrancephaly. It seems highly appropriate to ask how much of the central nervous system must be represented if there is to be CNS activation of the pituitary gland to release growth hormone. Through the cooperation of Profs. William Nyhan and Louis Gluck at the University Hospital of San Diego County, we have begun to explore this question in hydrancephalic infants. The data are preliminary but indicate that there is a constant concentration of growth hormone in blood, not varying with sleep or insulin administration. Arginine did induce a rise in one patient studied. The hydrancephalic infants having no cerebral cortex showed no electroencephalographic waves so that sleep could only be behaviorally adjudged. Hyperglycemia and Thyrotrophin. There is recent evidence that glucose loadTable
Patient
1 2 3 4 5 6 7 8 9 10
3.-Maximum Anorexia
Es% 19.2 5.6 8.6 1.1 3.1 1.2 1.5 9.6 1.0 1.0
Plasma HGH, IRI and Glucose in Ten Patients Nervosa During Oral Glucose Tolerance Tests* Max HGH (w/ml.) 36.5 28.4 26.7 5.0 8.7 6.4 > 40.0 > 40.0 16.5 1.0
(Time) (1) (1) (1) (2) (1) (1) (2) (‘/2) (5) t-j
MaxIRI (I*U/ml.) 255 51 122 33 60 186 17 338 67 108
( Time)
(2) (3) (1) (1) (1) (1) (‘/2) (1) (fi) (1)
With
Max Glucose
(mg./lOO ml.) 184 117 150 123 212 111 142 166 106 133
Time
(2) (1) (1) (S)
WI (1) W) (1) W) (Xl
* Oral glucose tolerance tests were performed using lOO-Gm. glucose load. Time in hours after glucose loading is indicated in parentheses, and in the first eight subjects a relatively early rise in HGH, as estimated from the peak reached, was observed. HGH reached maximum concentration before IRI in six instances.
896
VANDER
LAAN
ET AL.
ing tends not only to suppress growth hormone release but also corticotropin, even in Addison’s disease.lO The response is brief and not to normal concentrations but of very substantial magnitude. We have tried to suppress thyrotrophin in myxedema by glucose administration and observed no response. Postprandial suppression of growth hormone and corticotropin in health would favor the action of insulin, and postprandial bliss rather than stress has long been advised to patients by their physicians. It appears unneccessary for thyrotrophin to be suppressed for the full benefit of relaxation in the postprandial state to be experienced. SUMMARY
The release of growth hormone during sleep appears to be a clear example of the purposeful physiological activation of the endocrine system by the central nervous system. The slow wave activity of the cortex may reflect great activity in the limbic or other system rather than being the initiator. It is not clear that so-called stress activates growth hormone release by a different pathway than does sleep; one can only speak of a central nervous system activation. The studies of sleep reversal make clear that the activation of the pituitary gland is not a function of time but truly a phenomenon of sleep. Our studies relate this release to slow wave sleep and we record here evidence that hyperglycemia does not suppress the sleep release of growth hormone. We have studied anorexia nervosa as for us the most available disorder of malnutrition, and we call to attention the frequency with which glucose loading stimulates an early release of HGH. Although glucose tolerance tests may be called stress, it seems more appropriate in our opinion to note that the growth hormone release in response to hyperglycemia may serve a useful function in the malnourished, and we submit that the release of growth hormone may be stimulated by a highly sophisticated sensor, well aware of the nutritional needs of the body. In this sense the sluggish responses of the obese to stimuli of growth hormone release can be considered the opposite extreme of the response of the malnourished in whom release of growth hormone appears to occur with glucose loading. Although such responses have been called paradoxical they may serve a useful purpose. We feel it will be of interest to know whether release of growth hormone is a general response to glucose loading in the malnourished. If this proves to be the case there exists a relatively simple means of testing for malnutrition. It may be noted that other reports in which glucose loading was noted to stimulate growth hormone releasell-I” included disorders in which protein synthesis probably were impaired, although alternative explanations may have applied. What are the implications of the release of HGH during sleep for disease states? Will there be disease from failure of this mechanism? Does acromegaly represent a constant central nervous system drive to the pituitary or a primary glandular disorder? Did Macbeth fail to enter deep sleep which “no more knits up the ravelled sleave of care ?” Almost all the important questions remain to be answered, and we can only hope to have stimulated an interest in them.
897
GROWTH HORMONE RELEASE IN SLEEP
REFERENCES 1. Frantz, A. G.: Growth hormone in blood. In Astwood, E. B., and Cassidy, C. E. (Eds.): Clinical Endocrinology 2. New York, Grune & Stratton, 1968, p. 40. 2. Daughaday, W.: The adenohypophysis. In Williams, R. H. (Ed.): A Textbook of Endocrinology. Philadelphia, Saunders, 1968, p. 27. 3. Raben, M. S., and Hollenberg, C. H.: Effect of growth hormone in plasma fatty acids. J. Clin. Invest. 38:484, 1959. 4. Parker, D. C., Sassin, J. F., Mace, J. W., Gotlin, R. W., and Rossman, L. G.: Human growth hormone release during sleep: Electroencephalographic recording. J. Clin. Endocr. 29:871, 1969. 5. Herbert, V., Lau, K. S., Gottlieb, C. W., and Bleicher, S. J.: Coated charcoal immunoassay of insulin. J. Clin. Endocr. 25:1375, 1965. 6. Quabbe, H. J., Schilling, E., and Helge, H.: Pattern of growth hormone secretion during a 24 hour fast, J. Clin. Endocr. 26: 1173, 1966. 7. Londono, J. H., Gallaher, T. F., Jr., and Bray, G. A.: Effect of weight reduction, triiodothyronine, and stilbestrol on growth
hormone in obesity. Metabolism 18:986, 1969. 8. Glick, S. J., Roth, J., YaIow, R. S., and Berson, S. A.: The regulation of growth hormone secretion. Rec. Progr. Hormone Res. 21:241, 1965. 9. Pimstone, B. L., Wittmann, W., Hansen, J. D. L., and Murray, P.: Growth hormone and kwashiorkor: Role of protein in homeostasis. Lancet 2:779, 1966. 10. Rayyis, S. S., and Bethune, J. E.: Effect of blood glucose on ACTH secretion in man. Clin. Res. 18: 171, 1970. 11. Samaan, N., Cumming, W. S., Craig, J. W., and Pearson, 0. H.: Serum growth hormone and insulin levels in severe renal disease. Diabetes 15 : 546, 1966. 12. -, Pearson, 0. H., Gonzalez, D., and Llerena, 0.: Paradoxical secretion of growth hormone in patients with breast cancer. J. Lab. Clin. Med. 68:1011, 1966. 13. Perlroth, M. G., Tschudy, D. P., Waxman, A., and Odell, W. D.: Abnormalities of growth hormone regulation in acute intermittent porphyria. Metabolism 16:87, 1967.