Download 5-9_HypothalamicHormones_SzentgyorgyiR

Rita Szentgyörgyi
The function of the hypothalamic hormones
The hypothalamus:
The hypothalamus is a small but complex region of the brain located below the thalamus and
right above the brain stem. It has links with both the nervous system as well as the endocrine
system.
Its main role is to maintain the internal balance of the body, the homeostasis. To do this, it
helps control many of the body’s key processes: heart rate and blood pressure, body
temperature, fluid and electrolyte balance (food and water intake, hunger and thirst), body
weight, sleep cycles, sexual behavior and reproduction and most importantly the release of the
hormones by the pituitary gland.
Hypothalamic hormones:
When the hypothalamus receives a signal from the nervous system, it starts to secrete
neurohormones that control and regulate the secretion of pituitary hormones. The pituitary
gland consists of an anterior and a posterior lobe, each of which has distinct functions. The
anterior lobe secretes hormones that regulate a wide variety of bodily functions, while the
posterior lobe stores and releases hormones produced by the hypothalamus.
The hypothalamus has two major nuclei, the supraoptic and the paraventricular nuclei. The
cells in these nuclei secrete vasopressin (ADH) and oxytocin and transport them down the
axons to the posterior pituitary, where they are stored and released into the blood stream.
The hypothalamus releases several other hormones from its neurons into the blood in the
capillaries. From here they reach the portal veins to another capillary bed in the anterior part
of the pituitary. These hormones control the release of hormones from the pituitary gland.
They are called releasing and release-inhibiting hormones.
Effects of the hypothalamic hormones:
Releasing, release-inhibiting hormones:
 Thyrotropin-releasing hormone/TRH: stimulates the release of thyroid-stimulating
hormone/TSH (stimulates the release of thyroid hormones, which regulate
metabolism, energy and growth) and prolactin (stimulates breast milk production)
from anterior pituitary
 Dopamine: inhibits prolactin release from anterior pituitary
 Growth hormone-releasing hormone/GHRH: stimulates growth hormone/GH release
from anterior pituitary (controls normal physical development in children, metabolism,
healthy muscle and bone mass in adults)
 Somatostatin: inhibits GH and TSH release from anterior pituitary
 Gonadotropin-releasing hormone/GnRH: stimulates follicle-stimulating hormone/FSH
and luteinizing hormone/LH release from anterior pituitary (FSH and LH work
together to ensure normal functioning of the ovaries and testes)
 Corticotropin-releasing hormone/CRH: stimulates adrenocorticotropic
hormone/ACTH release from anterior pituitary (stimulates secretion of glucocorticoids
– cortisol - by the adrenal cortex during the body’s response to stress)
Vasopressin/antidiuretic hormone/ADH: regulates water levels in the body, affects blood
pressure and volume
Oxytocin: stimulates smooth muscle contractions of the uterus and lactation (letdown reflex),
controls aspects of some human behavior (recognition, trust, mother-infant bonding)