TriiodothyronineTriiodothyronine, also known as T3, is a thyroid hormone. It affects almost every physiological process in the body, including growth and development, metabolism, body temperature, and heart rate. Production of T3 and its prohormone thyroxine (T4) is activated by thyroid-stimulating hormone (TSH), which is released from the anterior pituitary gland. This pathway is part of a closed-loop feedback process: Elevated concentrations of T3, and T4 in the blood plasma inhibit the production of TSH in the anterior pituitary gland.
Magnocellular neurosecretory cellMagnocellular neurosecretory cells are large neuroendocrine cells within the supraoptic nucleus and paraventricular nucleus of the hypothalamus. They are also found in smaller numbers in accessory cell groups between these two nuclei, the largest one being the circular nucleus. There are two types of magnocellular neurosecretory cells, oxytocin-producing cells and vasopressin-producing cells, but a small number can produce both hormones. These cells are neuroendocrine neurons, are electrically excitable, and generate action potentials in response to afferent stimulation.
DiencephalonThe diencephalon (or interbrain) is a division of the forebrain (embryonic prosencephalon). It is situated between the telencephalon and the midbrain (embryonic mesencephalon). The diencephalon has also been known as the 'tweenbrain in older literature. It consists of structures that are on either side of the third ventricle, including the thalamus, the hypothalamus, the epithalamus and the subthalamus. The diencephalon is one of the main vesicles of the brain formed during embryogenesis.
Growth hormone–releasing hormoneGrowth hormone–releasing hormone (GHRH), also known as somatocrinin or by several other names in its endogenous forms and as somatorelin (INN) in its pharmaceutical form, is a releasing hormone of growth hormone (GH). It is a 44-amino acid peptide hormone produced in the arcuate nucleus of the hypothalamus. GHRH first appears in the human hypothalamus between 18 and 29 weeks of gestation, which corresponds to the start of production of growth hormone and other somatotropes in fetuses.
Hypothalamic–pituitary–thyroid axisThe hypothalamic–pituitary–thyroid axis (HPT axis for short, a.k.a. thyroid homeostasis or thyrotropic feedback control) is part of the neuroendocrine system responsible for the regulation of metabolism and also responds to stress. As its name suggests, it depends upon the hypothalamus, the pituitary gland, and the thyroid gland. The hypothalamus senses low circulating levels of thyroid hormone (Triiodothyronine (T3) and Thyroxine (T4)) and responds by releasing thyrotropin-releasing hormone (TRH).
Releasing and inhibiting hormonesReleasing hormones and inhibiting hormones are hormones whose main purpose is to control the release of other hormones, either by stimulating or inhibiting their release. They are also called liberins (ˈlɪbərᵻnz) and statins (ˈstætᵻnz) (respectively), or releasing factors and inhibiting factors. The principal examples are hypothalamic-pituitary hormones that can be classified from several viewpoints: they are hypothalamic hormones (originating in the hypothalamus), they are hypophysiotropic hormones (affecting the hypophysis, that is, the pituitary gland), and they are tropic hormones (having other endocrine glands as their target).
ForebrainIn the anatomy of the brain of vertebrates, the forebrain or prosencephalon is the rostral (forward-most) portion of the brain. The forebrain (prosencephalon), the midbrain (mesencephalon), and hindbrain (rhombencephalon) are the three primary brain vesicles during the early development of the nervous system. The forebrain controls body temperature, reproductive functions, eating, sleeping, and the display of emotions.
Periventricular nucleusThe periventricular nucleus is a thin sheet of small neurons located in the wall of the third ventricle, a composite structure of the hypothalamus. It functions in analgesia. It is located in the rostral, intermediate, and caudal regions of the hypothalamus. The rostral region aids in the production of both somatostatin and thyroid releasing hormone. The intermediate portion aids in production of thyroid releasing hormone, somatostatin, leptin, gastrin, and neuropeptide y. In humans and primates it also produces GnRH.
Tropic hormoneTropic hormones are hormones that have other endocrine glands as their target. Most tropic hormones are produced and secreted by the anterior pituitary. The hypothalamus secretes tropic hormones that target the anterior pituitary, and the thyroid gland secretes thyroxine, which targets the hypothalamus and therefore can be considered a tropic hormone. The term tropic is from Ancient Greek τροπικός (tropikós), in the sense "of or pertaining to a turn or change", meaning "causing a change, affecting"; this is the same origin as tropic and trope.
Energy homeostasisIn biology, energy homeostasis, or the homeostatic control of energy balance, is a biological process that involves the coordinated homeostatic regulation of food intake (energy inflow) and energy expenditure (energy outflow). The human brain, particularly the hypothalamus, plays a central role in regulating energy homeostasis and generating the sense of hunger by integrating a number of biochemical signals that transmit information about energy balance. Fifty percent of the energy from glucose metabolism is immediately converted to heat.
