ObjectiveTo determine whether serum inhibin A and inhibin B concentrations are lower in patients with luteal dysfunction than in women with normal luteal function.MethodsSerum samples were collected from seven healthy women with regular menstrual cycles. Serum samples on days +5 to +9 after the LH surge were collected from patients with luteal dysfunction. The diagnosis of luteal dysfunction was based on a luteal phase duration less than 11 days and a single midluteal progesterone level below 10 ng/mL. Serum levels of inhibin A, inhibin B, progesterone, estradiol (E2), FSH, and LH were measured.ResultsThe serum inhibin A levels were increased toward the late follicular phase. The levels reached a maximum during the midluteal phase, followed by a fall during the late luteal phase. The serum inhibin B levels were high during the follicular phases and the early luteal phase. The levels decreased during the midluteal and late luteal phases. Serum levels (mean ± standard error of the mean) of inhibin A in patients with luteal dysfunction were significantly lower than those in women during the midluteal phase (26.2 ± 2.9 compared to 41.9 ± 2.8 pg/mL;P< .01) in addition to the expected decrease in serum progesterone levels (6.3 ± 0.7 compared to 14.7 ± 1.2 ng/mL;P< .01). Serum inhibin B levels did not differ significantly between normal women and those with luteal dysfunction. There also were no significant differences in the E2, FSH, and LH levels.ConclusionLevels of inhibin A, but not of inhibin B, may reflect the human luteal function.