Lactotrophs

Lactotrophs are secretory cells of the anterior pituitary (adenohypophysis) that produce and release prolactin, a hormone essential for lactation and a range of other physiological processes. They originate from the oral ectoderm via Rathke’s pouch and are characteristically acidophilic on histology, making up roughly a minority of anterior pituitary cells, with estimates around 15–25%. Their number and activity can increase during pregnancy due to estrogen-induced lactotroph hyperplasia.

Prolactin release from lactotrophs is governed by hypothalamic control. Dopamine (hypothalamic “tuberoinfundibular” dopamine) tonically inhibits prolactin secretion through D2 receptors on lactotrophs. Sporadic stimuli such as thyrotropin-releasing hormone (TRH) can enhance prolactin release. Suckling or infant nursing reduces hypothalamic dopamine, triggering a prolactin surge that supports milk production. Estrogen also increases lactotroph proliferation and prolactin synthesis, contributing to physiologic changes during pregnancy.

The principal function of prolactin is to stimulate milk production in the mammary glands. It also has roles in immune regulation, osmoregulation, and metabolic processes, and it can modulate the reproductive axis by inhibiting gonadotropin-releasing hormone, contributing to lactational amenorrhea. Clinically, excess prolactin due to lactotroph adenomas (prolactinomas) or other causes leads to hyperprolactinemia, with symptoms including galactorrhea, amenorrhea, infertility in women, and reduced libido or hypogonadism in men. Diagnosis involves serum prolactin measurement and pituitary imaging; treatment typically uses dopamine agonists such as cabergoline or bromocriptine, with surgery or radiotherapy reserved for refractory or large tumors.