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Harrison's Principles of Internal Medicine, 18e
| Part 16. Endocrinology and Metabolism > Section 2. Disorders of Bone and Mineral Metabolism > |
Chapter 353. Disorders of the Parathyroid Gland and Calcium Homeostasis
Sections: Disorders of the Parathyroid Gland and Calcium Homeostasis: Introduction, Parathyroid Hormone, Parathyroid Hormone–Related Protein (PTHrP), Calcitonin, Hypercalcemia, Hypocalcemia, Further Readings.
Topics Discussed: calcium metabolism disorders; disorders of calcium and phosphorus homeostasis; parathyroid diseases.
Excerpt:"The four parathyroid glands are located posterior to the thyroid gland. They produce parathyroid hormone (PTH), which is the primary regulator of calcium physiology. PTH acts directly on bone, where it induces calcium resorption, and on the kidney, where it enhances calcium reabsorption and synthesis of 1,25-dihydroxyvitamin D [1,25(OH)2D], a hormone that increases gastrointestinal calcium absorption. Serum PTH levels are tightly regulated by a negative feedback loop. Calcium, acting through the calcium-sensing receptor, and vitamin D, acting through its nuclear receptor, reduce PTH release and synthesis. Additional evidence indicates that fibroblast growth factor 23 (FGF23), a phosphaturic hormone, can suppress PTH secretion. Understanding the hormonal pathways that regulate calcium levels and bone metabolism is essential for effective diagnosis and management of a wide array of hyper- and hypocalcemic disorders...."
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