Pulsatile gonadotrophin secretion in hyperprolactinaemic amenorrhoea an the response to bromocriptine therapy.

Serum gonadotrophin concentrations were measured every 15 min for 8 h in six patients before and at weekly intervals during initiation of bromocriptine treatment of hyperprolactinaemic amenorrhoea. Before treatment mean gonadotrophin levels were similar to those found in the normal follicular phase, but LH secretion was characterized by infrequent pulses of large amplitude. In three subjects the patterns of LH pulsatility and serum oestradiol levels returned to normal within 7 days of starting bromocriptine. The other three subjects responded with an increase in the frequency of LH pulses and mean LH levels, but little rise in oestradiol. Thus some hyperprolactinaemic subjects have a defect in the ovarian response to endogenous gonadotrophin stimulation, which may persist for a few weeks after return of prolactin levels to normal. The restoration of a normal rate of LH pulsatility with bromocriptine can occur without any change in serum oestradiol concentration.