Serum cortisol in women users of subdermal levonorgestrel implants

The aim of this study was to reveal changes in serum cortisol levels in users of subdermal levonorgestrel implants (Norplant). The study was undertaken on 18 regularly menstruating females subdermally implanted with 6 silastic rods, each containing 34 +or- 2 mg levonorgestrel, between days M0-M+4 of the menstrual cycle. Venous blood samples were collected between 10:00 and 11:00 a.m. under basal conditions, before and 1, 6, and 12 months after implantation. Sera were analyzed for cortisol by radioimmunoassay procedures. Mean +or- S.E.M. cortisol levels were 15.94 +or- 1.23, 10.20 +or- 0.84, 11.21 +or- 1.14, and 11.14 +or- 1.05 mcg prior to and 1, 6, and 12 months after implantation, respectively. All postimplantation values were significantly lower in comparison to basal levels. However, results obtained fell within the normal range of serum cortisol, with no subjects reporting symptoms of adrenocortical insufficiency.