Growth Hormone and TSH – Anterior Pituitary Hormones (Nursing)

00:00 Along with stimulating the posterior pituitary, the hypothalamus also secretes releasing and inhibiting hormones to the anterior pituitary to regulate hormone secretion. The anterior pituitary can release 6 different hormones into the blood. They include luteinizing hormone, follicle-stimulating hormone, thyroid-stimulating hormone, prolactin, growth hormone, and adrenocorticotropic hormone or ACTH. All 6 of these hormones are peptide hormones all but the growth hormone are going to activate their target cells by way of the cyclic AMP second messenger system. All but 2 of these hormones are tropic hormones that are going to regulate the secretion of another hormone. Growth hormone is referred to as a somatotropin because it is produced by somatotropic cells. It has direct actions on metabolism and indirect actions on growth promotion. The direct actions on metabolism by growth hormone include glucose sparing. Glucose-sparing actions decrease the rate of cellular glucose uptake and metabolism. So basically this is an anti-insulin effect. Growth hormone can also trigger the liver to break down glycogen into glucose and it can increase blood levels of fatty acids for use as fuel and encourage cellular protein synthesis. Indirect actions on growth by the growth hormone include the growth hormone triggering the liver, skeletal muscles, and bones to produce insulin-like growth factor or IgFs. IgFs then stimulate cellular uptake of certain nutrients that are used to synthesize DNA and proteins that are needed for cell division.

02:18 They also are going to be responsible for formation of collagen and deposition of bone matrix.

02:27 Growth hormone can also stimulate cells to enlarge and divide, but major targets are going to be the bone and the skeletal muscle. Growth hormone release or inhibition is going to be chiefly regulated by the hypothalamic hormones on somatotropic cells. For example, growth hormone-releasing hormone or GHRH is going to stimulate the release of growth hormone.

03:00 This is usually triggered by low blood growth hormone or by low glucose. It can also be triggered by high amino acid levels in the blood. Secondly, we have growth hormone-inhibiting hormone or GHIH. This is referred to as somatostatin because it inhibits the release of growth hormone. This is usually triggered by increase blood levels of growth hormone and also increase IGF levels. Another hormone is going to be ghrelin or the hunger hormone. This is going to also stimulate growth hormone release. The next anterior pituitary hormone that we'll discuss is thyroid-stimulating hormone. This is a tropic hormone that is also sometimes referred to as thyrotropin and it is produced by thyrotropic cells. This stimulates the normal development and the secretory activity of the thyroid. Its release is going to be triggered by thyrotropin-releasing hormone in the hypothalamus. It is inhibited by rising blood levels of thyroid hormone that then act on the pituitary and the hypothalamus. It is also inhibited by the growth hormone-inhibiting hormone. So taking a closer look at the negative feedback loop for the thyroid-stimulating hormone, we find that the hypothalamus is going to release thyrotropin-releasing hormone which goes to the anterior pituitary. This stimulates the release of thyroid-stimulating hormone which then acts on the thyroid gland causing the thyroid to release thyroid hormones which will then go to our target cells. However, increasing blood levels of thyroid hormone act as a negative feedback loop and inhibit the release of thyrotropin-releasing hormone from the hypothalamus as well as thyroid-stimulating hormone from the anterior pituitary.