PTH-dependent a
Hypoparathyroidism
• Parathyroid agenesis
• PTH gene mutations
• Postoperative (transient or permanent)
• Autoimmune
– Isolated
– Combined with multiple endocrine deficiencies
• Activating mutations of the calcium sensing receptor
• Developmental abnormalities of the parathyroids (Di George syndrome, etc.)
• Neonatal hypocalcaemia
• Infiltrative processes (iron overload, Wilson’s disease, metastases)
• Radiation therapy
• Hypomagnesemia
• Hypermagnesemia
PTH-independent b
PTH resistance
• Pseudohypoparathyroidism (1a, 1b, 1c, 2)
• Hypomagnesemia
Alterations of vitamin D metabolism
• Acquired deficiency of vitamin D
– Lack of sunlight exposure
– Nutritional deficiency
– Malabsorption
– End-stage liver disease and cirrhosis
– Anticonvulsants
• Hereditary disorders of Vitamin D metabolism
– 1α hydroxylase deficiency
– Vitamin D-dependent rickets type 1
– Vitamin D-dependent rickets type 2
Miscellaneous causes
• Increased osteoblastic activity
– Hungry bone syndrome (post-parathyroidectomy, post-thyroidectomy for Graves’ disease)
– Osteoblastic metastases
• Drugs reducing serum calcium levels
– Forcarnet
– Intravenous bisphosphonate therapy
• Hyperphosphatemia
• Large transfusions of citrate-containing blood
• Acute pancreatitis
• Rhabdomyolysis
• Acute critical illness
In our patient, on the basis of serum phosphorus and intact PTH concentrations, all causes of hypocalcemia associated with reactive secondary hyperparathyroidism could be excluded. Therefore, we focused on PTH-dependent causes. The decreased levels of magnesium raised the possibility that this might be the cause. Hypomagnesemia may be due to gastrointestinal disorders, renal loss, endocrine and metabolic disorders (Table 26.2) [4].
Table 26.2
Causes of magnesium deficiency
Gastrointestinal disorders • Prolonged nasogastric suction/vomiting • Acute and chronic diarrhea • Intestinal and biliary fistula • Malabsorption syndromes • Extensive bowel resection or bypass • Acute hemorrhagic pancreatitis • Protein-calorie malnutrition • Primary intestinal hypomagnesemia |
Endocrine and metabolic disorders • Diabetes mellitus • Phosphate depletion • Primary hyperparathyroidism (hypercalcemia) • Hypoparathyroidism (hypercalciuria, hypercalcemia caused by overtreatment with vitamin D) • Primary aldosteronism • Hungry bone syndrome • Excessive lactation |
Renal loss • Primary renal hypomagnesemia (genetic defects in Mg transport) • Chronic parenteral fluid therapy • Osmotic diuresis (glucose, urea, mannitol) • Hypercalcemia • Alcohol • Diuretics (e.g., furosemide) • Cisplatin • Amphotericin B • Pentamidine • Cyclosporin • Tacrolimus • Proton pump inhibitors • Metabolic acidosis • Chronic renal disorders with magnesium deficiency • Mutation of mitochondrial RNA
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