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How does the hypothalamus control hormones released by the pituitary gland?

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Diagram comparing action potential conduction in myelinated and unmyelinated axons, showing a neuron with labeled cell body, myelin sheath, nodes of Ranvier, and the flow of electrical signals along each type of axon. — nervous system In a myelinated axon, the myelin sheath prevents the local current (small black arrows) from flowing across the membrane. This forces the current to travel down the nerve fibre to the unmyelinated nodes of Ranvier, which have a high concentration of ion channels. Upon stimulation, these ion channels propagate the action potential (large green arrows) to the next node. Thus, the action potential jumps along the fibre as it is regenerated at each node, a process called saltatory conduction. In an unmyelinated axon, the action potential is propagated along the entire membrane, fading as it diffuses back through the membrane to the original depolarized region.

The hypothalamus regulates the pituitary gland through complex nervous and chemical pathways, acting as a critical bridge between the nervous system and the endocrine system.2

Anterior Pituitary Regulation

The hypothalamus controls the anterior pituitary by secreting neurohormones—such as thyrotropin-releasing hormone and growth-hormone-releasing hormone—from neurons in the median eminence. These substances are released into a specialized capillary network known as the hypophyseal-portal circulation, which delivers them directly to the anterior pituitary to stimulate or inhibit the secretion of its hormones. For instance, dopamine and somatostatin act as inhibitors for specific pituitary hormones.12

Posterior Pituitary Regulation

The posterior pituitary is regulated differently. Hormones like vasopressin and oxytocin are synthesized in the hypothalamic nuclei, packaged into granules, and transported down axons through the infundibular stalk. These hormones are stored in nerve terminals within the posterior lobe and are released into the general circulation in response to neural stimuli.2