- Discussion:
- parathyroid hormone is 84 aa petide made & secreted from chief cells in 4 parathyroid glands;
- all actions of PTH are either directly or indirectly involved w/ maintaining serum ionic Ca concetration (see
Ca hemostatsis);
- it stimulates the differentiation of osteoclastic progenitor cells and effects bone resorption thru stimulation of
osteoclasts (thru
indirect mechanisms - not direct receptor mediation);
- enhances synthesis of
1,25-dihydroxyvitamin D, (increase GI absorption of Ca & renal reabsorption of calcium);
- over secretion may cause
hypercalcemia and
hyperparathyroidism;
- specific effects:
- bone:
- indirectly increases the number of
osteoclasts;
- increase the efflux of calcium and phosphorous from bone;
- gut: indirectly increase the intestinal Ca absorption (thru vit D);
- kidney:
- increases tubular reabsorption of Ca from kidney (increases c-AMP in proximal tubule);
- decreases in tubular reabsorption of phosphate which leads to significant phosphaturia (resulting in borderline
hypophosphatemia);
- note that normal phosphorous reabsorption is about 85%;
Humoral hypercalcemia of cancer: identification of a novel parathyroid hormone-like peptide. Broadus AE N Engl J Med 1988;319:556-63.
Parathyroid hormone: chemistry, biosynthesis, and mode of action. Potts JT Jr, Kronenberg HM, Rosenblatt M. Adv Protein Chem 1982;35:323-96.
The Effects of Parathyroid Hormone and Alendronate Alone or in Combination in Postmenopausal Osteoporosis
The Effects of Parathyroid Hormone, Alendronate, or Both in Men with Osteoporosis
Combination of local and systemic parathyroid hormone enhances bone regeneration.
Parathyroid hormone--a drug for orthopedic surgery?
One Year of Alendronate after One Year of Parathyroid Hormone (1–84) for Osteoporosis.
Daily and Cyclic Parathyroid Hormone in Women Receiving Alendronate.
