[Gonadotropin and plasma cyclic nucleotides]

Plasma cyclic nucleotides in some physiological conditions were measured in normal women and the changes of cyclic AMP were studied after the loading of gonadotropins in normal and castrated women. We demonstrated a circadian rhythm of cyclic AMP and its variation during menstrual cycle in normal women and also demonstrated its significant increase in pregnant women. But there was no significant variation of plasma cyclic GMP levels in those physiological conditions. Plasma cyclic AMP was increased by the simultaneous administration of HMG and HCG in both normal and castrated women. However, individual administration of HMG or HCG demonstrated that it was HCG that caused that increase in plasma cyclic AMP even in castrated women. To examine the extragonadal effects of HCG, cortisol, triiodothyronine (T3), thyroxine (T4) in the plasma were measured after the loading of HCG. The plasma cortisol level was influenced by HCG in neither normal nor castrated women. HCG did not cause any change of T3 or T4 in normal women; however it caused a marked increase in T3 with a small decrease in T4 in castrated women.