Effect of oestriol on the oscillation of circulating gonadotrophins in post-menopausal women during sleep.

The effect of oestriol on the rapid oscillation of circulating FSH and LH levels during sleep was investigated by administering oestriol (E3: 2 mg/day) orally for 3 mth to 3 healthy post-menopausal women who experienced frequent hot flushes. Before treatment and at the end of the third mth of treatment, blood samples were drawn the length of sleep, and serum FSH and LH level were measured by radioimmunoassay. Fluctuations of serum FSH and LH levels were recorded and the pulses were defined as a 20% increase of hormone concentration over nadir. The increase of hormone levels of pulses recorded before treatment were compared with those recorded during treatment (the end of the third mth). No significant difference was found in serum FSH levels, yet a difference was found in serum LH levels. The pulses during the treatment nights were lower than those in the pre-treatment nights (P less than or equal to 0.01). The levelling of the pulses of serum LH levels under oestriol treatment is probably an expression of the influence of oestriol on the hypothalamus-anterior-pituitary system.