• Pituitary Control: Hypothalamus. Hypothalamic control is chemically mediated through hormonal release mediation.

  • Hypothalamic hormonal synthesis is followed by hormones moving through the portal vascular system to the pituitary stalk and to the pituitary anterior lobe.

  • Pituitary stalk interruption causes:

    • Decreased release from the anterior pituitary of: GH, LH, FSH, TSH, and ACTH

    • Increased prolactin (hypothalamic influence is normally inhibitory for prolactin secretion)

  • Hypothalamic ablation:

    • Results in decreased levels of GH, LH, FSH, TSH, ACTH, AVP and oxytocin

    • and an increase in prolactin.

• Secretion Control:  by hypothalamic factors (peptides)  include:

  • Growth hormone-releasing hormone (GHRH):   dominant GH release influence (+)

  • Somatostatin is an inhibitory hormone for GH release (-)

  • Luteinizing hormone-releasing hormone (LHRH), also called gonadotropin-releasing hormone (GnRH), controls LH and FSH.

  • Thyrotropin-releasing hormone (TRH) controls TSH release and influences prolactin release.

  • Corticotropin-releasing hormone (CRH) as well as other factors control ACTH release..

  • Dopamine is major prolactin inhibitory influence (PIF).

     

    • Action of corticotrophin-releasing hormone (CRH) on cells of the adrenal cortex

      "Action of corticotrophin-releasing hormone (CRH) on cells of the adrenal cortex. CRH binds to membrane receptors (R), which are coupled to adenylate cyclase (AC) by stimulatory G proteins (Gs). Adenylate cyclase is stimulated and cAMP rises in the cell. cAMP activates protein kinase A (PKA), which then phosphorylates proteins (P-Proteins) involved in stimulating ACTH secretion and the expression of the POMC (proopiomelanocortin) gene. The proteolytic processing of POMC occurs in the secretory granulas where it is split into several hormones, ACTH (adrenocorticotrophic hormone) and Beta-LPH (Beta-lipotropin). " Courtesy of Robert H. Parsons, Ph.D., Rensselaer Polytechnic Institute, used with permission

 

 

Adapted from Table 328-1: Biller, Beverly, M. K. and Daniels, Gilbert, H. Neuroendocrine Regulation and Diseases of the Anterior Pituitary and Hypothalamus, In Harrison's Principles of Internal Medicine 14th edition, (Isselbacher, K.J., Braunwald, E., Wilson, J.D., Martin, J.B., Fauci, A.S. and Kasper, D.L., eds) McGraw-Hill, Inc (Health Professions Division), 1998, p. 197

Reference: Fitzgerald, P.A. and Klonoff, D.C. Hypothalamic and Pituitary Hormones, in Basic and Clinical Pharmacology, (Katzung, B. G., ed) Appleton-Lange, 1998, pp 603-618.

Reference: Biller, Beverly M. K. and Daniels, Gilbert, H. Neuroendocrine Regulation and Diseases of the Anterior Pituitary and Hypothalamus, In Harrison's Principles of Internal Medicine 14th edition, (Isselbacher, K.J., Braunwald, E., Wilson, J.D., Martin, J.B., Fauci, A.S. and Kasper, D.L., eds) McGraw-Hill, Inc (Health Professions Division), 1998, pp 1972-1998