PTH stimulates calcium cations (Ca++) and phosphorous (Pi) release from bone breakdown, Ca++ reabsorption (but Pi excretion) from renal tubules. PTH stimulates renal conversion of 25(OH) vitamin D to 1,25(OH)2 vitamin D, which then further stimulates bone breakdown, Ca++ reabsorption/ Pi excretion from renal tubules, in addition to enhancing gut absorption of Ca++ and Pi. 25(OH) vitamin D is the product of liver metabolism of vitamin D that enter the body from the gut and sunlight. PTH secretion from the parathyroid gland is triggered by low serum Ca and high serum magnesium levels, and is suppressed by high serum Ca and vitamin D levels.
HYPOPARATHYROIDISM
✿ Dysfunctional pth gland (1°)
✧ autoimmune
⁎ isolated hypoparathyroidism
⁎ polyglandular autoimmune syndrome
✧ iatrogenic
⁎ thyroidectomy
⁎ parathyroidectomy
⁎ neck dissection
⁎ radiation
⁎ transfusion hemosiderosis
✧ infiltration
⁎ granulomas
⁎ hemochromatosis
⁎ wilson's disease
⁎ metastatic cancer
⁎ riedel's thyroiditis
✧ infection
✧ congenital
⁎ familial hypoparathyroidism
⁎ digeorge's syndrome
⁎ kenny-caffey syndrome
⁎ kearns-sayre syndrome
⁎ melas syndrome
⁎ gata3 gene mutation
✿ Dysregulated pth gland (2°)
✧ overstimulated ca sensing receptor
⁎ hypo/hyper-magnesemia
HYPERPARATHYROIDISM
✿ Overactive pth gland (1°)
✧ hereditary
⁎ familial 1° hyperparathyroidism
⁎ men syndromes
✧ tumor
⁎ hyperplasias
⁎ adenomas
⁎ carcinomas
✧ iatrogenic
⁎ radioiodine therapy
⁎ radiation
✧ drug-induced
⁎ lithium
✿ Overstimulated pth gland (2°)
✧ hypocalcemia
✧ vitamin d deficiency
✧ chronic kidney disease
✿ Autonomous pth gland (3°)
✧ chronic kidney disease
✿ Ectopic pth production
✧ carcinomas (ovarian, lung)
✧ neuroectodermal tumor
✧ rhabdomyosarcoma
