Effect of Synthetic Progestins on Pituitary Gonadotrophin Excretion

Abstract

The effect of the daily administration of 2.5 and 5 mg of norethisterone acetate on pituitary gonadotrophin excretion was studied in 6 cycles in 3 normal females. Inhibition of ovulation was demonstrated in 2 of the subjects by the failure to note a significant rise in pregnanediol excretion in the latter half of the cycle. In 5 of the 6 cycles there was inhibition of the midcycle rise in LH excretion as measured by the ventral prostate assay. Total gonadotrophin excretion, as measured by the rat testis weight, was also reduced, but to a lesser degree. It was concluded that these small dosages of norethisterone acetate can affect ovulation via inhibition of pituitary gland function.