inhibitinghormoner

Inhibitinghormoner refers to a class of hypothalamic signals that suppress the secretion of hormones from the anterior pituitary gland. These inhibitory signals complement releasing hormones, together forming the regulatory axis that controls pituitary output. The term covers various substances that reduce or prevent the release of pituitary hormones in response to physiological need, circadian rhythms, or feedback from peripheral glands.

The principal examples include somatostatin, also called growth hormone-inhibiting hormone (GHIH), which primarily inhibits growth hormone and thyroid-stimulating hormone secretion from pituitary corticotrophs and thyrotrophs. Dopamine, historically termed prolactin-inhibiting factor or prolactin-inhibiting hormone, acts mainly to suppress prolactin release from lactotrophs. In several species, gonadotropin-inhibitory hormone (GnIH), now often discussed as RFamide-related peptide (RFRP) in mammals, reduces gonadotropin release by acting on GnRH neurons or directly on pituitary gonadotrophs.

Mechanistically, these inhibitors are released into the hypothalamo-hypophyseal portal circulation and bind to specific receptors on pituitary cells, triggering intracellular signaling that lowers cyclic AMP or otherwise dampens secretory pathways. They operate alongside releasing hormones to fine-tune hormone levels, contributing to growth, metabolism, reproductive function, and lactation.

Clinical relevance varies: somatostatin analogs are used to treat acromegaly and certain hormone-secreting tumors; dopamine agonists treat hyperprolactinemia. Ongoing research explores GnIH/RFRP pathways as potential targets for fertility regulation and other endocrine conditions.