Plasma levels of medroxyprogesterone acetate (MPA), sex-hormone binding globulin, gonadal steroids, gonadotrophins and prolactin in women during long-term use of depo-MPA (Depo-Provera®) as a contraceptive agent

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Abstract
The functional state of the hypothalamo-pituitary-gonadal axis and the concentrations of MPA [medroxyprogesterone acetate] in the peripheral blood were evaluated during very long-term use of depo-medroxyprogesterone acetate (DMPA) as a contraceptive agent. The concentrations of MPA, sex-hormone binding globulin (SHBG) and the different pituitary and gonadal hormones in the peripheral blood were measured in nine 26-41 yr old women. They had for 4.4-10.6 yr (mean 8.9 yr) been receiving DMPA i.m. in a dose of 150 mg every 12th wk as a contraceptive. Blood samples were obtained immediately before an injection of DMPA, 2 wk later, and again immediately before the next injection. SHBG was measured by radio-electroimmunoassay; MPA, gonadal and pituitary hormones by radioimmunoassay. The estradiol levels, even after very long-term use of DMPA, were still within the normal range for the early follicular phase. Gonadotropins and prolactin were within the normal range for eumenorrheic women, as was the concentration of SHBG. MPA did not accumulate in the plasma. The changes in the plasma levels of estradiol, MPA and SHBG after each injection disappeared within 12 wk. Even up to 10 yr, use of DMPA in a dose of 150 mg i.m. every 12th wk as a contraceptive agent evidently does not induce hormonal changes different from those seen after the very 1st injection.