Effect of prostaglandin F_2α on the luteal phase of the cycle in nonpregnant women

Eleven healthy nonpregnant female volunteers were treated with prostaglandin F_2α as the THAM salt in aqueous solution administered intravaginally. Human chorionic gonadotropins (HCG) was also administered to 9 of these women prior to or following the prostaglandin therapy to simulate secreting trophoblast. It was considered that luteolysis occurred if serum progestin declined to preovulatory levels, if there was no increase of serum progestin levels following HCG, and if there was shortening of the menstrual cycle by at least three days. Plasma LH, progesterone, 17-hydroxyprogesterone, 20α-dihydroprogesterone, and prostaglandin were measured by radioimmunoassay techniques. When administered early in the luteal phase, PGF_2α did not alter the length of the cycle. When administered in midluteal phase followed by HCG, there was an increase in cycle length and in serum progesterone levels. If no HCG was given, the cycle length was increased after PGF_2α. When administered late in the cycle, the progesterone levels rose, but the cycle length remained unaltered despite HCG. The prostaglandin plasma levels varied significantly among the patients despite a uniform route/dose administration. However, with low plasma levels, there was evidence of increased progesterone production, while with high plasma levels, progesterone output rapidly diminished. The side effect accompanying elevated PGF_2α plasma levels were pronounced.