Plasma concentration of gonadotrophins, oestrogens and progesterone in thyrotoxic women.

Plasma levels of luteinizing hormone (LH), follicle stimulating hormone (FSH), oestrogen and progesterone were measured daily in 15 thyrotoxic women in the reproductive age for 28 to 30 consecutive days before commencement of therapy and for a similar period following restoration of the euthyroid state. Five of these patients had secondary amenorrhoea whilst the other 10 had hypomenorrhoea. Twelve healthy volunteer eythyroid women of similar age and parity, with no history of menstrual abnormality, served as controls. The levels of both gonadotrophins (LH and FSH) and oestrogen were found to be significantly raised in all thyrotoxic patients in comparison with levels in the euthyroid female controls (P less than 0.001). "Mid cycle" LH and FSH peaks were present in thyrotoxic patients who were still menstruating whilst they were absent in those who developed amenorrhoea. Plasma oestrogen concentration rose to a peak on the day before the surge of LH (and FSH) in all euthyroid frmale controls as well as in thyrotoxic patients who were still menstruating. In contrast, oestrogen peaks occurred without ensuing LH (and FSH) peaks in thyrotoxic patients who had developed amenorrhoea, suggesting a failure of the positive feed-back mechanism. The levels and patterns of plasma progesterone in thyrotoxic subjects who were still menstruating were similar to those of euthyroid controls. However, no significant circulating plasma progesterone was detected in thyrotoxic subjects who were amenorrhoeic. The levels and patterns of all of these hormones (gonadotrophins, oestrogen and progesterone) became normal after restoration of euthyroid state and normal menstruation.