The influence of hyperthyroidism on the hypothalamic-pituitary-gonadal axis

We have investigated the function of the hypothalamic-pituitary-gonadal (H- P-G)-axis in patients with severe, untreated Graves' disease. We studied 7 male and 6 female healthy volunteers and 7 male and 7 female patients with Graves' disease. Hormone profiles were developed by blood sampling every 10 min for an 8 hour period. In women this was done in the early follicular p hase of menstrual cycle. LH-. FSH-, and PRL levels were measured using immu noradiometric assays and testosterone (T), estradiol (E2), sex-hormone bind ing globulin (SHBG), and progesterone (P) were measured with standard assay s The pulsatility of LH, FSH and PRL was calculated using the programmes Pu lsar, Cluster and Desade. The temporal relationship of plasma LH, FSH, and PRL pulses was also investigated using specific concordance analysis. Data were evaluated by means of non-parametric statistics. LH-secretion was incr eased in all hyperthyroid patient while FSH-secretion was increased in hype rthyroid men only Pulsatile characteristics of LH- and FSH-secretion (frequ ency, peak shape) in patients were not different from controls. No change i n PRL-secretion was shown. Significant copulsatility occurred between LPI a nd FSH, and LH and PRL. This was more pronounced in hyperthyroid than in he althy study subjects. Plasma levels of steroid hormones and sex-hormone-bin ding globulin were significantly (p < 0.005) increased in hyperthyroid men. Free Androgen Index was significantly (p < 0.005) decreased in hyperthyroi d males. No Ether auto immune diseases were noticed. Our results indicate t hat the function of the H-P-G axis is not impaired in hyperthyroid patients , but gonadotropin levels are increased. Hyperthyroid men show relative pri mary gonadal insufficiency that may be due to exaggerated SHBG levels. The copulsatility of LH and FSH, and of LH and PRL was confirmed birth in patie nts and controls.