neurohypophyseal

Neurohypophyseal refers to the neurohypophysis, the posterior portion of the pituitary gland that forms the neural part of the organ and is connected to the hypothalamus by the infundibulum. It develops from neural ectoderm and serves primarily as a storage and release site for neurohormones produced in the hypothalamus.

The posterior pituitary contains the axon terminals of magnocellular neurons whose cell bodies reside in the hypothalamic nuclei, mainly the supraoptic and paraventricular nuclei. The hormones vasopressin (antidiuretic hormone, ADH) and oxytocin are synthesized in these neurons, transported down their axons, and are stored in Herring bodies within the posterior pituitary. Secretion is triggered by neural signals and delivered directly into the systemic circulation through the posterior pituitary’s capillary network.

Regulation of neurohypophyseal secretion is driven by hypothalamic inputs responding to osmotic balance, blood volume, and hormonal or sensory stimuli. Osmoreceptors, baroreceptors, and tactile cues such as nipple stimulation influence the firing rate of hypothalamic neurons, thereby controlling release of ADH and oxytocin.

Physiological roles include: vasopressin promoting water reabsorption in the kidney collecting ducts (and, at higher concentrations, vasoconstriction via vascular receptors); oxytocin stimulating uterine contractions during labor and milk ejection during lactation, with additional roles proposed in social bonding and reproductive behavior.

Clinical relevance includes central diabetes insipidus, caused by ADH deficiency or disrupted secretion, leading to polyuria and polydipsia, and the syndrome of inappropriate antidiuretic hormone secretion (SIADH), characterized by excessive ADH release and water retention. Histologically, the neurohypophysis contains pituicytes and a dense capillary network with stored hormone-containing secretory granules.