Anabolic effect of pth

The secretion of hypothalamic, pituitary, and target tissue hormones is under tight regulatory control by a series of feedback and feed- forward loops. This complexity can be demonstrated using the growth hormone (GH) regulatory system as an example. The stimulatory substance growth hormone releasing hormone (GHRH) and the inhibitory substance somatostatin (SS) both products of the hypothalamus, control pituitary GH secretion. Somatostatin is also called growth hormone-inhibiting hormone (GHIH). Under the influence of GHRH, growth hormone is released into the systemic circulation, causing the target tissue to secrete insulin-like growth factor-1, IGF-1. Growth hormone also has other more direct metabolic effects; it is both hyperglycemic and lipolytic. The principal source of systemic IGF-1 is the liver, although most other tissues secrete and contribute to systemic IGF-1. Liver IGF-1 is considered to be the principal regulator of tissue growth. In particular, the IGF-1 secreted by the liver is believed to synchronize growth throughout the body, resulting in a homeostatic balance of tissue size and mass. IGF-1 secreted by peripheral tissues is generally considered to be autocrine or paracrine in its biological action.

Our data show that PTH can increase biochemical indicators of bone formation in the presence of pretreatment with the potent bisphosphonate, alendronate. This agrees with the majority of data generated in the rodent model of osteoporosis 12–14 but is distinct from data in the aged ewe 15 and a recent investigation using a PTH analog with preceding and ongoing alendronate therapy in the rodent. 16 These differences highlight the fact that animal models may not always be representative of human processes. Our pilot study indicates that in humans, the anabolic effect of daily subcutaneous PTH should not be abolished by alendronate. The combination of PTH and alendronate, therefore, remains a valid approach to the treatment of osteoporosis.

Anabolic effect of pth

anabolic effect of pth


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