Calcium-lowering hormones

Sites of Production of Calcium-Lowering Hormones 2.1. The Pabathyboid Glands... 

Detection and Measurement of Calcium-Lowering Hormones 5.1. Bioassay Pboceduees... 

Several animal species have been used in the biological assay of calcium-lowering hormones. For reasons of size, the rat is most commonly used, although mice have been claimed to be more responsive to human thyrocalcitonin preparations (S2). For studies of the course of thyro-calcitonin action in which serial blood samples were required, both pigs (C5) and goats (F4) have been used. For assessment of the potency of hoimone preparations, bioassay in rats is in general satisfactory. 

Under this therapy, menses will continue. The risk of thromboembolic disorders is increased and that of myocardial infarction probably lowered. Hormone treatment can be extended for 10 y or longer. Before menopause, daily calcium intake should be kept at 1 g (contained in 1 L of milk), and 1.5 g thereafter. 

Monkeys are considered the best substitutes for humans in meaningful studies of calcium metabolism wherein ionised calcium is hormonally controlled within normal limits by parathyroid and thyrocalcitonin. Low doses of thyrocalcitonin administered to Macaca cynomologus only lowered total calcium whereas higher doses depressed both total and ioruc calcium levels [120]. Thyrocalcitonin also lowered total and ionic calcium in the serum of intact rats but not to the same extent as after parathyroidectomy. Parathyroid hormone extracts given to the same parathyroidectomised group elevated both total and ionised calcium [70]. Another study on parathyroidectomised rats revealed a depression of all three serum calcium fractions (protein-bound, diffusible-complexed and ioruc) which was reversed on administration of parathyroid hormone. 

The main role of the human thyroid gland is production of thyroid hormones (iodinated amino acids), essential for adequate growth, development, and energy metaboHsm (1 6). Thyroid underfunction is an occurrence that can be treated successfully with thyroid preparations. In addition, the thyroid secretes calcitonin (also known as thyrocalcitonin), a polypeptide that lowers excessively high calcium blood levels. Thyroid hyperfunction, another important clinical entity, can be corrected by treatment with a variety of substances known as antithyroid dmgs. 

From preliminary in vitro experiments using rat renal slices, it appears that the hormone directly affects renal calcium transport. If insulin is the mediator of the hypercalciuria, it might be possible to reduce urinary calcium loss by lowering the intake of in-sulinogenic foods. This would be especially important in those individuals with a marked calciuric response to such foods. 

There seems to be no metabolic control exerted on hepatic 25-hydroxylase and so all of the available cholecalciferol is converted. Hydroxylation in the kidney however is an important control point being regulated by PTH, and indirectly therefore by calcium and phosphate concentrations. Stimulation of la-hydroxylase by PTH is via a cyclic AMP (cAMP) -dependent mechanism and longer-term regulation of the activity of this enzyme is via induction mediated by other hormones such as oestrogens, cortisol and growth hormone. Typically, the plasma concentration of 1,25 dihydroxy vitamin D is in the range 20-60 ng/1, that is approximately 1000-times lower than that of its precursor. 

A role for a collagenase, presumably fibroblast-type collagenase, in bone resorption has been indicated by studies employing the Searle A-carboxyl alkyl synthetic collagenase inhibitor CI-1 (compound (197) in Table 8.18) and its less potent stereoisomer CI-2 (compound (198) in Table 8.18) [207]. Cultured embryonic mouse calvaria treated with parathyroid hormone exhibit loss of calcium and show pronounced collagen resorption. CI-1 inhibited the collagen resorption in a dose-dependent manner at significantly lower concentrations than CI-2, but had only a small effect on calcium loss. This inhibitory effect was reversible and not due to inhibitor cytotoxicity. 

Calcitonin a peptide hormone secreted by the thyroid gland that lowers plasma calcium levels by increasing the deposition of bone. 

Mechanism of Action An antibiotic that forms complexes with DNA, inhibiting DNA-directed RNA synthesis. May inhibit parathyroid hormone effect on osteoclasts and inhibit bone resorption. TherapeuticEffect Lowers serum calcium and phosphate levels. Blocks hypercalcemic action of vitamin Dand action of parathyroid hormone. Decreases serum calcium. 

While they are often prescribed, the lower costs of codeine, ACE inhibitors, beta-blockers, thyroid hormones, calcium blockers, and benzodiazepines keep them off the list of top sales. Conversely, the higher cost of erythropoietins, antineo monoclonal antibodies, angiotensin II antagonists, antiarthritis drugs, and bisphosphonates put them on the list of top sales but not top prescriptions. 

Spironothiazid is a diureteic and an ALDOSTERONE antagonist. This means that it suppresses the water retaining actions of the hormone ALDOSTERONE while lowering water retention by lowering electrolytes (potassium, sodium, and calcium). The advantage of the combination is that the potassium absorption effect by the spironolactone can be mediated by the hydrochlorthiazide. Because of this, some of the potassium loss side effects can be avoided. This is probably a safer choice than LASIX though any diuretic use should be medically monitored. Thiazides also lead to a lower loss of calcium. 

Calcitonin is a peptide hormone produced in the thyroid gland that serves to lower serum calcium and phosphate levels by inhibiting bone resorption. Calcitonin has been used in the treatment of a variety of diseases, such as primary hyperparathyroidism, Paget s disease, and postmenopausal osteoporosis [99,100]. Salmon calcitonin has a longer half-life than human calcitonin. Salmon calcitonin, 3.6 kDa, is available as a nasal formulation that contains only benzalkonium chloride as a preservative, without an absorption enhancer, and as a parenteral product for injection. The direct effect of benzalkonium chloride on the nasal mucosa is under... 

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