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 hyperprolactinaemi a in the pathogenesis of galactorrhoea, amenorrhoea and possibly prolactino mas. Design. Descriptive study. Setting. Commercial Centre Family Planning Clinic and King Edward VIII Hosp ital, Durban, South Africa. Subjects. Seventy-four women on injectable cont raceptives comprised the study group. Thirty-nine of these women were on DM PA and 35 on NET EN. The control group comprised 62 women. Women with medic al conditions or medications that affected prolactin secretion as well as l actating and pregnant women were excluded from the study. Blood samples wer e obtained by venepuncture under controlled, standard conditions. Serum pro lactin levels were determined by enzyme-linked immunosorbent assay. Results. The overall mean serum prolactin level in the study group was 266 mIU/ml. In the control group the mean serum prolactin level was 245 mu IU/m l. There was no significant difference between the two groups (P = 0.39). T he mean serum prolactin level among women on DMPA was 226 mu IU/ml compared with 310 mu IU/ml among those on NET EN. Basal prolactin levels were signi ficantly increased in women on NET EN compared with the control group (P = 0.03). There was no significant difference in basal prolactin levels betwee n 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. Co nsequently NET EN may cause chronic hyperstimulation of anterior pituitary lactotrophs and may therefore predispose users to the development of prolac tinomas. The risk, however, is probably minimal.