Combined oral contraceptives affect liver mitochondrial activity.

Objectives: To examine liver mitochondrial function in women using combined oral contraceptives (COCs) containing ethinylestradiol.

Methods: A breath test after oral administration of 1 mg/kg (13)C-alpha-ketoisocaproic acid ((13)C-KICA) and 20 mg/kg L-leucine was performed twice: (i) in 15 women on day 14, 15, 16, 17 or 18 of COC intake, and between day 1 and 5 of the withdrawal bleeding; and (ii) in 15 regularly menstruating females not taking hormonal contraceptives: during the luteal phase, between the 18th and the 22nd day of the cycle, and again between day 1 and 5 of the menstruation.

Results: In women on COCs the maximum (13)C elimination in breath air (Dmax) was higher (26.