Hyperprolactinemia is a prolactin level above the reference range. Prolactin is the anterior pituitary hormone that drives milk production, made by the pituitary cells called lactotrophs. It is unusual among the anterior pituitary hormones in being held under continuous inhibition by the hypothalamus rather than driven by it. That fact organises the whole topic: the causes are the things that interrupt or bypass this inhibition, and the clinical picture follows from what the excess prolactin does to the gonadal axis (the hypothalamic and pituitary hormones that stimulate the ovaries or testes) and from the space a pituitary tumour occupies.
A reader new to the topic can start with regulation and causes, which explain why the level rises, and then follow the order below: the tumour and its presentation, galactorrhea and hypogonadism, diagnosis, treatment.
- Prolactin Regulation and Causes of Hyperprolactinemia: how dopamine holds prolactin in check, which signals raise it, and the full range of causes, from physiological states and drugs to lesions that interrupt the dopaminergic pathway.
- Prolactinoma and the Clinical Features of Hyperprolactinemia: what a prolactinoma is, how it differs by size and sex, and how the clinical picture divides into hormone-induced and tumour-induced features in women, in men and before puberty.
- Galactorrhea and Hypogonadism in Hyperprolactinemia: galactorrhea as persistent breast discharge, why it needs at least some estrogen and is therefore absent in frank hypogonadism, and how hyperprolactinemia suppresses the GnRH pulse generator.
- Diagnosis of Hyperprolactinemia: how the other causes are excluded first, and how the prolactin level, the imaging and the laboratory pitfalls of the high-dose hook effect and macroprolactinemia are read together.
- Treatment of Hyperprolactinemia: who needs treatment, dopamine agonists as first-line therapy, withdrawal of therapy, when surgery is chosen, prolactinoma in pregnancy and drug-induced hyperprolactinemia.