Increased dopamine turnover in women with polycystic ovary syndrome

European Journal of Obstetrics & Gynecology and Reproductive Elsevier

EUROBS

Biology, 33 (1989) 229-234

229

00831

Increased dopamine turnover in women with polycystic ovary syndrome C. Segos I, M. Markianos * and D. Aravantinos Athens Universiiy Medical School,

’

’ Gynaecologic Clinic, Alexandra Hospital, and 2 Psychiatric Eginition Hospital, Athens, Greece

Accepted

for publication

24 February

Clinic,

1989

summary The main dopamine metabolite, homovanillic acid (HVA), was measured in urine samples from 35 women with polycystic ovary syndrome (PCO) and in 38 normal menstruating women of the same age range. In both groups the plasma levels of LH, FSH, prolactin and testosterone were also measured. HVA excretion was significantly increased in women with PCO. Plasma levels of LH correlated negatively (r = -0.6268, 2a < 0.001) to urinary HVA in the group of normal women. This correlation did not exist in the women with PCO. The results suggest that there is a disturbance of the inhibitory influence of dopamine on LH secretion in women with the syndrome, which is not due to a deficient synthesis or utilization of dopamine. Polycystic ovary Testosterone

syndrome;

Dopamine

turnover;

Homovanillic

acid;

Prolactin;

Gonadotrophin;

Introduction The pathophysiology of the polycystic ovary syndrome (PCO) is in its greater part known, but is aetiology remains obscure. The main hormonal features of the syndrome are the high androgen production and the elevated plasma levels of luteinizing hormone. The high LH levels raise the question of an alteration of the LH regulating mechanisms in PCO, on the hormonal or on the neurotransmitter level. Regarding neurotransmitters that may participate in the regulation of LH, dopamine (DA), serotonin (5hydroxy-tryptamine, 5-HT) and noradrenaline have been discussed. In normal women, there are indications that DA exerts an inhibi-

Correspondence: Dr. M. Markianos, Athens University Hospital, Vas.Sophias 74, Athens 11528, Greece..

Medical

0028-2243/89/$03.50

B.V. (Biomedical

0 1989 Elsevier Science Publishers

School,

Psychiatric

Division)

Clinic,

Eginition

230

tory action on LH release, since DA infusion or L-dopa administration reduces plasma LH [l-3]. Women with PCO, show an exaggerated suppression of LH during DA infusion [4,5], while the administration of metoclopramide, a DA receptor blocker, does not elicit an LH response [6]. A decreased dopaminergic control of LH secretion has thus been hypothesized in PCO. Shoupe and Lobo [7] reported lower than normal urinary excretion of the main DA metabolite homovanillic acid (HVA) in a small group of women with PCO, and suggested a decreased DA turnover. However, the exaggerated LH suppression by DA was not confirmed by Barnes et al. [8], who suggested no major alterations of dopaminergic activity in PCO. Dopamine deficiency could also be disputed by the lack of effect of drugs that increase dopaminergic activity on plasma LH in women with the syndrome. Indeed, both bromocryptine and L-dopa do not cause the expected reduction of plasma LH in PC0 [9-121. In this study, we measured the urinary concentrations of the main metabolite of dopamine, homovanillic acid (HVA), as an index of whole body DA turnover, in a large group of women with PC0 and compared them to the values of a group of normally menstruating women of the same age range. In both groups we measured the levels of prolactin (PRL), LH and FSH, and testosterone (T), and searched for possible correlations between hormonal levels and the excretion of the dopamine metabolite. Subjects and methods

The women with PC0 of the study were selected from the outpatient population of women who came for examination to the University Gynaecologic Clinic of the Alexandra Hospital in Athens. The criteria for inclusion in the study were: (a) anovulatory situation established around the menarche; (b) appearance of polycystic ovaries in the ultrasonic examination; and (c) hirsutism present. In addition, all patients of the study had an LH to FSH ratio greater than 2. The age range was 18 to 30 years. They had not menstruated for at least the last three months, and did not take any drugs during that period. The control group was compiled of normally menstruating women in the same age range, with a cycle of 26-30 days who did not take contraceptives or any other drugs. Blood and urine samples were taken from them before the 9th or after the 20th day of the cycle. From all subjects a blood sample was taken between 09.00 and 11.00 a.m., and morning urine for two consecutive days. The plasma and urine aliquots were kept at - 35O C until estimations. We chose to collect morning urine instead of 24-hour specimens for the following reasons: (a) it simplifies the protocol substantially, increasing thus the collaboration and the reliability of the sample; (b) it minimizes the influences of physical activity during the day on the excretion of biogenic amine metabolites; we thus collect urine samples under the most homogeneous conditions for patients and controls; (c) it minimizes the influences of other factors like mood changes during the day, or intake of food and beverages, which may influence neurotransmitter turnover. HVA was measured by a gas-chromatographic method which has been used for several years in our laboratory, with inter- and intra-assay variation coefficients

231

below 10%. Shortly HVA is extracted from 0.5 ml acidified urine aliquots into ether, and reacted with trifluoroacetic anhydride and hexafluoroisopropanol to form the fluorinated derivative, which is injected in a GC-system with electron capture detector and integrator. Each sample, in duplicates, was also worked out with pure HVA, added at the beginning of the procedure. The mean value of the two urine samples from each subject was taken for calculations. PRL, LH, FSH and T were measured using the radioimmunoassay kits of Biodata, Milan, Italy. PRL is expressed in ng/ml, and 1 ng PRL corresponds to 0.023 mIU of the WHO 75/504 IRP. LH and FSH mIU are referred to mIU of the 2nd IRP-HMG, and T is expressed in nmol/ml plasma. For the statistical evaluation of the data we used the Students t-test for unpaired data for comparisons of HVA excretion and hormone levels between patients and controls. Age and mean body weight were compared using the non-parametric Mann-Whitney U-test. The Pearson product-moment correlation coefficient was used for detecting possible relations of HVA to the plasma hormone levels in the two groups, and the non-parametric Spearman correlation coefficient to relate the variables measured to the age and mean body weight.

Results The mean values of the variables measured are given in Table I. The patients had a 20% overweight in the mean. The plasma levels of T and LH were highly significantly elevated in the patients group compared to the group of normal women. PRL levels were also higher in the PC0 group. From the 35 women studied, six had PRL levels over 20 ng/ml, i.e., the incidence of hyperprolactinaemia in the group was 17%, which is in good agreement with most studies on the subject. FSH levels were not different from normal, and the ratios LH/FSH were higher in the PC0 group.

TABLE

I

Mean values (standard deviations in parentheses) of hormone levels in plasma and homovanillic acid in urine of normal women and women with polycystic ovary syndrome. Statistical evaluation by Student’s t-test for unpaired observations, except age and mean body weight, where the non-parametric MannWhitney U-test was used. Variable/units

Normal

Age, years Mean body weight (%) PRL (ng/ml) T (pmol/nQ LH (mIU/ml) FSH (mIU/ml) Ratio LH/FSH HVA (nmol/mg treat.)

24.2 (3.5) 98.8 (8.2) 9.1 (4.6) 2.13 (0.7) 12.1 (4.4) 9.3 (3.4) 1.4 (0.6) 14.7 (4.6)

NS, not significant.

(n = 38)

PCOS (n = 35) 23.0 (3.7) 121.0 (22.0) 13.3 (7.3) 3.85 (1.6) 21.9 (9.4) 8.8 (3.0) 2.8 (1.5) 20.0 (6.7)

t

-

2P 1.3968 4.9833 2.9133 5.9313 5.7907 0.7466 5.3164 3.9360

NS 0.001 0.005 0.001 0.001 NS 0.001

232

40

0 E c

. : : . ;

20

a > I

i. . .

! :

1.

-z *

j.

7

! : !

10

PC0

CONTROLS

Fig. 1. Urinary

homovanillic acid in a group of 38 normal women and 35 patients syndrome. The difference is significant at the 0.001 level.

with polycystic

ovary

” = 36 y

=

20.9

- 0.6.x 2a

LH

c

0.001

mlU/ml

. 20 r

=-

.6266

10

10

20 HVA

nmol/mQ

30 creatinine

Fig. 2. Correlation between plasma LH levels and urinary homovanilhc acid excretion in a group of normal women. The samples were taken before the 9th or after the 20th day of the cycle. The correlation is not significant in the group of women with PC0 syndrome.

233

The excretion of HVA in urine of the women with PC0 syndrome, was significantly higher compared to normals (2p < 0.001, Fig. 1). In the group of normal women, HVA correlated negatively to the LH levels (r = -0.6268, df = 36, 2a < 0.001, Fig. 2) but this correlation did not exist in the PC0 group (r = -0.0582, NS). We tested for possible correlations between weight, expressed as percent of mean body weight, and HVA excretion or plasma hormone levels using the non-parametric Spearman correlation coefficient. No significant correlations could be found in either group of women.

Discussion The main findings of this study are in the increased excretion of HVA in women with PC0 compared to normal women, and the negative correlation of plasma LH to urinary HVA in the group of normal women, which does not exist in the PC0 group. Shoupe and Lobo [7] reported low and, later, Barnes, Artal and Lobo [S] normal HVA excretion in women with PCO. Both studies were designed to answer several questions on the relation of dopamine to the syndrome, but, in respect to HVA excretion, we think that the number of subjects in both studies (seven PC0 and six controls, and five PC0 and five controls) was too small to draw final conclusions. Urinary HVA represents both the central and the peripheral dopamine turnover, and the contribution of the central nervous system is considered to be about one third of the total amount excreted [13]. For the questions of this study this is not of great importance, since both central and peripheral dopamine may inhibit LH secretion. The results show clearly that the dopamine synthesis and utilization in women with PC0 is not deficient but rather increased. In addition, the correlation between dopamine turnover and plasma LH levels which exists in normal women, is disturbed in women with the syndrome. The inability of dopamine to inhibit LH secretion in PC0 does not seem to be due to a deficient synthesis or utilization of the neurotransmitter. Much more the search should be addressed to factors that modulate dopaminergic inhibition of LH and of prolactin, and as such have been proposed, among others, estrogens and opioids [6,14-161. The abundance of dopamine in the syndrome we found, can explain satisfactorily the lack of effect of dopamine agonists on LH in women with PC0 [9-121, since the defect, if related to dopamine, is not due to a lack in the synthesis or utilization of the neurotransmitter. Although the data from humans indicate an inhibitory action of DA on LH release, there is evidence from animal experiments (rats) that DA may exert a stimulatory role in the regulation of GnRH release [17]. If such an action could be hypothesized in humans, the elevated LH levels in PC0 could be attributed to the increased dopamine turnover we report here, but the low to normal FSH levels that are found in the syndrome are difficult to explain. Finally, regarding PRL plasma levels and HVA excretion, they did not correlate significantly either in the group of normals or in the PCOS group. The HVA values of the subjects with hyperprolactinaemia in the PC0 group (n = 6) did not differ

234

from those of the normoprolactinaemic PC0 (n = 29), but this question further evaluation in a larger sample of women with hyperprolactinaemia.

needs

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