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Essentials of Diagnosis
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Tetany, carpopedal spasms, tingling of lips and hands, cramps, irritability
Chvostek sign and Trousseau phenomenon
Hypocalcemia with low serum parathyroid hormone (PTH); serum phosphate high; alkaline phosphatase normal; urine calcium excretion reduced
Serum magnesium may be low
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General Considerations
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Acquired hypoparathyroidism
Most commonly caused by anterior neck surgery, occurring after total thyroidectomy in about 25% of patients transiently, and in about 4% of patients permanently
Risk is higher for patients undergoing total thyroidectomy (especially large goiters) or surgery for Graves disease, patients over age 50, and when fewer than 2 parathyroid glands are identified at surgery
Risk of permanent postoperative hypoparathyroidism can be reduced during thyroid surgery by taking parathyroid glands with suspected vascular damage and autotransplanting them into the sternocleidomastoid muscle
Permanent hypoparathyroidism
May occur after the resection of multiple parathyroid adenomas
In cases of "hungry bone syndrome" (transient hypoparathyroidism after the surgical removal of a single parathyroid adenoma for primary hyperparathyroidism due to suppression of the remaining normal parathyroids and accelerated remineralization of the skeleton), hypocalcemia can be quite severe, particularly in patients with preoperative hyperparathyroid bone disease and vitamin D or magnesium deficiency
Neck irradiation is a rare cause
Autoimmune hypoparathyroidism may be isolated or combined with other endocrine deficiencies
Parathyroid deficiency may be caused by
Magnesium deficiency causes functional hypoparathyroidism
Hypomagnesemia
Most commonly caused by alcoholism, diuretics, intestinal malabsorption, and proton pump inhibitors
Can also be caused by
Certain antibiotics (aminoglycosides, amphotericin, and pentamidine)
Epithelial growth factor inhibitors (panitumumab, cetuximab) for colon cancer
Mild hypomagnesemia stimulates PTH secretion; however, more severe hypomagnesemia (< 1.2 mg/dL) inhibits PTH secretion
Also causes resistance to PTH in bone and renal tubules
Symptomatic hypoparathyroidism may be precipitated by a proton pump inhibitor, since absorption of calcium decreases with reduced stomach acidity
Congenital hypoparathyroidism
Causes hypocalcemia beginning in infancy; however, it may not be diagnosed for many years
Since hypoparathyroidism can be familial, screening is suggested for family members of any patient with idiopathic hypoparathyroidism
Genetic testing is suggested for the following
DiGeorge syndrome is another cause of congenital hypoparathyroidism, along with congenital cardiac and facial anomalies
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Manifestations of hypocalcemia vary from subtle to life-threatening
Patients may complain of fatigue, irritability, depression, anxiety, cognitive impairment or "brain fog", lethargy, and paresthesias in the circumoral area, hands, and feet
More severe manifestations include muscle weakness or cramps, carpopedal spasm, convulsions, tetany, laryngospasm, and stridor
Brain calcifications in the basal ganglia and cerebral cortex can cause Parkinsonian symptoms or choreoathetosis
Chronic hypocalcemia with hyperphosphatemia can cause ...