Prolactin levels in South African women on injectable progestogen contraceptives

Objective. To demonstrate the effect of depot medroxyprogesterone acetate (DMPA) and norethisterone oenanthate (NET EN) on basal prolactin levels with a view to investigating the role of progestogen-induced hyperprolactinaemia in the pathogenesis of galactorrhoea, amenorrhoea and possibly prolactinomas. Design. Descriptive study. Setting. Commercial Centre Family Planning Clinic and King Edward VIII Hospital, Durban, South Africa. Subjects. Seventy-four women on injectable contraceptives comprised the study group. Thirty-nine of these women were on DMPA and 35 on NET EN. The control group comprised 62 women. Women with medical conditions or medications that affected prolactin secretion as well as lactating and pregnant women were excluded from the study. Blood samples were obtained by venepuncture under controlled, standard conditions. Serum prolactin levels were determined by enzyme-linked immunosorbent assay. Results. The overall mean serum prolactin level in the study group was 266 μIU/ml. In the control group the mean serum prolactin level was 245 μIU/ml. There was no significant difference between the two groups (P = 0.39). The mean serum prolactin level among women on DMPA was 226 μIU/ml compared with 310 μIU/ml among those on NET EN. Basal prolactin levels were significantly increased in women on NET EN compared with the control group (P = 0.03). There was no significant difference in basal prolactin levels between the control group and women on DMPA (P = 0.43). Conclusion. The use of NET EN was associated with a significant increase in serum prolactin levels, although they remained within the normal range. Consequently NET EN may cause chronic hyperstimulation of anterior pituitary lactotrophs and may therefore predispose users to the development of prolactinomas. The risk however, is probably minimal.