Effects of Oral Contraceptives on Diurnal Profiles of Insulin and IGFBP-1 in Endurance Athletes with Menstrual Disturbances

Abstract

1914 Amenorrhea in athletes is associated with endocrine changes reflecting energy deficiency. Among those are decreased secretion of insulin and increased secretion of insulin-like growth factor binding protein 1 (IGFBP-1). PURPOSE: The aim of this study was to evaluate effects of oral contraceptives (OC) on the diurnal pattern of insulin and IGFBP-1 in endurance female athletes. METHODS: Age- and BMImatched groups of endurance athletes with oligo-/amenorrhea (n = 9), regularly cycling athletes (n = 8) and sedentary controls (n = 8) were compared with respect to 24-hour hormonal profiles of insulin and IGFBP-1 before and after 10 months of treatment with a low-dose monophasic, combined OC. RESULTS: Before OC, the 24-hour hormone profile of insulin was significantly lower in athletes with menstrual disturbances compared with controls. During treatment, insulin secretion increased in all groups, although not significantly, and the differences between groups were abolished. Diurnal secretion of IGFBP-1 was highest among oligo-/amenorrheic athletes at baseline and lowest in the control subjects. OC treatment increased the 24-hour IGFBBP-1 profile in regularly menstruating subjects. The largest increase was found in controls (p < 0.001), and a less increase in the regularly cycling athletes (p < 0.05), whereas no change was seen in athletes with menstrual disturbances. There was no difference in IGFBP- 1 secretion between groups during OC treatment. CONCLUSION: OC treatment increased diurnal secretion of IGFBP-1 in regularly menstruating subjects, whereas the secretion was unchanged in oligo-/amenorrheic athletes. Athletes with menstrual disturbances had elevated diurnal secretion of IGFBP-1 and decreased secretion of insulin at baseline compared with controls. These metabolic alterations were abolished by OC treatment. It is suggested that OC treatment may have favorable metabolic effects in oligo-/amenorrheic athletes.