Types of Anterior Pituitary Cells:
1) Somatotrophs
Secrete Equine Growth Hormone (eGH) aka Somatotropin .
Equine Growth Hormone is the most plentiful anterior pituitary hormone. Its main function is to promote synthesis and secretion of small protein hormones called Insulin like Growth Factors (IGF) aka Somatomedins . IGF is secreted by cells of the liver, skeletal muscle, cartilage, bones, and other tissues in response eGH. IGF stimulate general body growth and regulate aspects of metabolism.
Functions of eGH :
1) eGH stimulates the release of IGF which causes cells to grow and multiply therefore increasing the growth rate of the skeleton and skeletal muscles of younger horses. In mature horses, eGH helps maintain muscle mass and mass of bones. It also promotes healing of injuries and tissue repair. 2) IGFs enhance lipolysis in adipose tissue resulting in increased use of released fatty acids for ATP production by body cells. 3) IGFs influence carbohydrate metabolism by decreasing glucose uptake decreasing the use of glucose for ATP production. This function spares glucose so that it is available to neurons for ATP production in times of glucose scarcity. It is thought that IGFs also may stimulate liver cells to release glucose into the blood.
Control of eGH :
eGH is released from the somatotrophs of the anterior pituitary every few hours especially during sleep. Release is controlled primarily by 2 hypothalamus hormones: Growth Hormone-Releasing Hormone (GHRH) Growth Hormone-Inhibiting Hormone (GHIH) . A major regulator of GHRH and GHIH is blood glucose levels. Low blood glucose (hypoglycemia) stimulates release of GHRH. Hyperglycemia simulates the release of GHIH.
2) Thyrotrophs
Secrete Thyroid-Stimulating Hormone (TSH) aka Thyrotropin .
Functions of TSH :
Stimulates synthesis and secretion of Triiodothyonine (T3) and Thyroxine (T4) both produced by the thyroid gland.
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