Regression of pituitary microadenoma during and following bromocriptine therapy: persistent defect in prolactin regulation before and throughout pregnancy.

During 5 years of clinical, endocrinologic, and radiologic observations in a woman with a microprolactinoma treated medically with bromocriptine for 29 months, serial hypothalamic-pituitary studies revealed a defect in lactotrope function after prolactin (PRL) concentrations and ovulation were restored to normal. This defect persisted throughout a spontaneously conceived pregnancy in which the PRL, estradiol, and progesterone levels were subnormal, while, the dehydroepiandrosterone sulfate levels were normal and estriol concentrations were elevated. Levels of the beta subunit of human chorionic gonadotropin (hCG) were close to and slightly above the normal ranges. These observations are consistent with a role for PRL, interacting with hCG, in the control of estrogen and progesterone secretion by the fetoplacental unit. Lactation was initiated and maintained post partum. Pituitary function and PrL responses to suckling suggested improved lactotrope function 22 to 25 months after withdrawal of bromocriptine. The impaired lactotrope function, therefore, did not preclude normal implantation, pregnancy maintenance, onset of parturition, fetal development, and lactation.