Effects of Norplant [subdermal implants] on serum levels of beta-endorphin: prolactin and gonadotropin

50 parous women were enrolled in a longitudinal study of the effect of Norplant subdermal [long acting levonorgestrel] implant on serum levels of gonadotropins [FSH and LH], prolactin [PRL] and beta- endorphin [beta-Ed] for 5 years user. All of them had children. 40 women only completed the study. 10 married parous women not using hormonal contraception volunteers as control. The Norplant users and the control were similarly studied. Starting by day 5 of their cycle until the next menses, three samples were taken [postmenstrual, midcycle and premenstrual phases]. These samples were collected at the end of one, two up to five years since insertion of Norplant. There was definite improvement in the bleeding pattern with time. Marked inhibition were noticed in the serum levels of LH and FSH surge during the first three years, then elevated to be in the range of normal levels in the last two years. Serum PRL and beta-Ed levels lost there normal cyclicity and sustained at a low or high tonic levels all over the study. This study suggested that, Norplant acts mainly by inhibiting the ovulation through suppressing the LH and FSH surge while, the anovulation may be the cause of cesation of normal pulsatility for both serum beta-Ed and PRL