No effect of ethinylestradiol treatment on melatonin secretion in healthy pubertal girls

The present study investigated the impact of high estrogen doses on melatonin blood concentrations in healthy young girls. Melatonin secretion was investigated in 7 girls (chronological age 13.2 +/- 0.2 years; bone age 12.8 +/- 0.2 years) before and during treatment with ethinylestradiol (EE2, daily dose 0.5 mg/d orally) aimed at the reduction of final prospective height in familial tall stature. Melatonin, LH, FSH, E2 and EE2 were measured by radioimmunoassay. In all subjects, LH and FSH were completely suppressed, but melatonin secretion, day/night plasma values as well as the area under the curve (AUC) remained unchanged under pharmacological administration of ethinylestradiol. We therefore conclude that melatonin secretion is not affected by pharmacological doses of the synthetic estrogen derivative ethinylestradiol in healthy young girls. The decrease of melatonin blood concentrations during puberty is not caused by increasing concentrations of estrogens but must be due to some other process.