Pituitary is the proximal endocrine gland which links the Central Nervous System for NEUROENDOCRINE control of both metabolism and reproduction. These NEUROHORMONES control synthesis and secretion of Anterior Pituitary hormones which control Thyroid, Adrenal, Gonads, Growth & Lactation.
NEUROHORMONES are synthesized in specialized neurosecretory cells which are concentrated within Hypothalamus. Neurohormones reach Anterior Pituitary Gland via a specialized portal vascular system. Nerve fibers originating in neurosecretory cells terminate in the MEDIAN EMINENCE of the hypothalamus located below third ventricle.
Anterior Pituitary Hormones secreted (PEPTIDES) –>
- Adrenocorticotropin (ACTH)
- Follicle Stimulating Hormone (FSH)
- Luteinizing Hormone (LH)
- Thyroid Stimulating Hormone (TSH)
- Growth Hormone (GH)
- Prolactin
| NEUROHORMONE | PITUITARY SITE OF ACTION | EFFECT | EXTRAHYPOTHALAMIC SYNTHESIS | EXTRAPITUITARY EFFECTS |
| THYROTROPIN RELEASING HORMONE (TRH) | Thyrotroph Prolactotroph | Stimulate Stimulate | Brain and Gastrointestinal Tract | YES |
| GROWTH HORMONE RELEASING HORMONE (GRH) | Somatotroph | Stimulate | Pancreas | YES |
| SOMATOSTATIN (SS) | Somatotroph Thyrotroph | Inhibit Inhibit | Brain, Pancreas and Gastrointestinal Tract | YES |
| GONADOTROPIN-RELEASING HORMONE (GnRH) | Gonadotroph | Stimulate | Gonads | YES |
| CORTICOTROPIN-RELEASING HORMONE (CRH) | Corticotroph | Stimulate | Pancreas | YES |
| PROLACTIN-INHIBITING HORMONE (PIH) | Prolactotroph | Inhibit | Gonads | |
| DOPAMINE | Prolactotroph | Inhibit | Adrenal medulla and Nervous system | YES |
Regulation of most anterior Pituitary function depends primarily on positive stimulatory signals from hypothalamus EXCEPT biogenic amine dopamine and PROLACTIN INHIBITING HORMONE.
ANTERIOR LOBE OF PITUITARY –> connected to hypothalamus via HYPOPHYSEAL PORTAL VASCULAR SYSTEM.
POSTERIOR LOBE OF PITUITARY –> Is an elongated extension of the ventral hypothalamus. (Supraoptic and paraventricular nuclei)
Posterior Pituitary hormones (PEPTIDES)–>
- Antidiuretic Hormones (ADH) / Vasopressin
- Oxytocin
Although ADH and Oxytocin are synthesized in discrete cells, producer cells for each hormone are located in both supraoptic and paraventricular nuclei areas. Each peptide is synthesized as part of a larger precursor protein and after processing remains noncovalently bound to a portion of the precursor termed NEUROPHYSIN.
NEUROHORMONES OUTSIDE THE HYPOTHALAMUS
Neurohormones initially identified in the hypothalamus by their effects on anterior Pituitary function are also synthesized in several locations throughout the body, esp
- Within Gastrointestinal tract
- Other central nervous system areas
“YOU NEED SELF-CONTROL IN OUT OF CONTROL WORLD” – James C Collins
Concept Maps 