Prolactin secretion in epileptic subjects treated with phenobarbital: sex differences and circadian periodicity

Circulating basal prolactin (PRL) levels were evaluated in 126 subjects of both sexes with partial or generalized epilepsy, who were treated with phenobarbital (PB) alone or in combination with either phenytoin or benzodiazepines. A significant increase in PRL levels was observed in male, but not in female, patients compared with a sex- and age-matched healthy volunteer group. Circadian PRL secretion, studied in six male epileptic patients on PB monotherapy and in nine normal subjects, showed comparable 24-h PRL mean values and a preserved PRL surge during the night in both groups; however, a statistically significant additional peak was found in male epileptic subjects during the late afternoon. The cosinor analysis of the data, used to evaluate PRL rhythmicity, showed a disruption of the 24-h periodicity in epileptic subjects, while the 12-h periodicity was maintained. These results indicate that central and/or peripheral mechanisms involved in PRL secretion control are more sensitive to PB alone or in combination with other antiepileptic drugs in male than in female subjects. However, the changes of PRL secretion we found were small and unrelated to the different clinical conditions.