Hormone opposing effects

When the actions of one hormone oppose the effects of another, the result is antagonism. For example, insulin decreases blood glucose and promotes the formation of fat. Glucagon, on the other hand, increases blood glucose and promotes the degradation of fat. Therefore, the effects of insulin and glucagon are antagonistic. 

Parathyroid hormone-related protein receptor is a GPCR that acts via a Gas (and elevation of cAMP) or via Gaq (to activate PLC, increase IP3 and thence increase cytosolic Ca2+). PTH increases bone resorption and reabsorption of Ca2+ in the kidney with consequent elevation of blood Ca2+. Calcitonin, which binds to a GPCR that acts via a Gas to elevate C.AMP, has opposing effects to those of PTH. 

The opposing effects of the hormones insulin and glucagon on glycogen metabolism. 

Compounds that mimic the effects of sex steroids in some tissues, while at the same time can oppose endogenous hormone action in other tissues. 

Recently, leaders in the pharmaceutical industry have developed a list of desired properties for a fourth generation of SERMs (Table 2). In general, future SERMs must oppose endogenous hormone action in the breast and reproductive system while displaying full estrogenic effects in the cardiovasculature, bone and central nervous systems. Additional criteria are that fourth generation compounds possess superior bioavailability compared with existing SERMs and have... 

One of the principles of the use of hormones in oncology is based on the fact that the growth of tumors which occur in hormone-sensitive tissues may be inhibited by hormones with opposing actions, by hormone antagonists, or by agents that inhibit the synthesis of the stimulatory hormone. Other hormone treatments are based on less specific antimitotic effects. 

Which one of the following statements concerning vitamin D is correct A. Chronic renal failure requires the oral administra tion of 1,25-dihydroxycholecalciferol. B. It is required in the diet of individuals exposed to sunlight. C. 25-Hydroxycholecalciferol is the active form of the vitamin. D. Vitamin D opposes the effect of parathyroid hor mone. E. A deficiency in vitamin D results in an increased secretion of calcitonin. Correct answer = A. Renal failure results in the decreased ability to form the active form of the vitamin, which must be supplied. The vitamin is not required in individuals exposed to sunlight. 1,25-dihydroxycholecalciferol is the active form of the vitamin. Vitamin D and parathyroid hormone both increase serum calcium. A deficiency of vitamin D decreases the secretion of calcitonin. 

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