Fluctuations of serum bile acid concentrations during the menstrual cycle.

Fasting primary bile acid conjugates were measured in 44 women by radioimmunoassay methods. Bile acid values were significantly greater in the 21 women who were in the first half of the menstrual cycle than in the 23 women in whom blood was sampled during the second half of the cycle. Similar measurements were made at weekly intervals after menstruation in five subjects; increased values were observed in the first week. It is concluded that serum bile acid values fluctuate during the menstrual cycle.