Modulation of immunoreactive somatomedin-C levels by sex steroids

Among 28 menstruating women tested once randomly during the cycle, somatomedin-C (Sm-C) values were lower in the 10 women in normal follicular phase than in the 10 women in normal luteal phase or the 8 women with hyperandrogenism. Among these 28 subjects, Sm-C showed a positive correlation with testosterone and a positive correlation of borderline significance with oestradiol. A positive correlation was also evidenced between Sm-C and in progesterone among the 20 women of this group who were not hyperandrogenic. In 5 other normal women investigated daily throughout an entire menstrual cycle, Sm-C concentrations were higher during days +4 to +9 of this cycle (luteal phase) than during days -3 to -8 (follicular phase). In another group of 21 healthy women, Sm-C values were increased during medroxyprogesterone acetate (150 mg trimestrially) treatment. In 7 normal men, Sm-C decreased during ethinyl-oestradiol (1 mg daily for 5 days) administration. These findings suggest that circulating Sm-C levels are modulated by variations of sex steroids which occur during the menstrual cycle as well as by pharmacological doses of oestrogens and progestagens.