Hypomagnesemia differential diagnosis

• Genetic defect causing end organ resistance to the action of parathyroid hormone (PTH)
• Heterozygous GNAS inactivating mutations that reduce expression or function of Gα_s
• Genetic mutation disrupts both receptor-mediated activation of adenylyl cyclase and receptor-independent activation of the enzyme.

• ↓ 1,25 Dihydroxy vitamin D
• ↓ Urinary cAMP
• ↓ Urinary phosphate

• Genetic defect causing end organ resistance to the action of parathyroid hormone (PTH).
• Familial– heterozygous deletions in STX16, NESP55, and/or AS exons or loss of methylation at GNAS

• ↓ 1,25 Dihydroxy vitamin D
• ↓ Urinary cAMP
• ↓ Urinary phosphate

• Genetic defect causing end organ resistance to the action of parathyroid hormone (PTH).
• Heterozygous GNAS inactivating mutations that reduce expression or function of Gα_s
• Genetic mutation disrupts receptor-mediated activation of adenylyl cyclase but does not affect receptor-independent activation of the enzyme.

• ↓ 1,25 Dihydroxy vitamin D
• ↓ Urinary cAMP
• ↓ Urinary phosphate

• Genetic defect causing end organ resistance to the action of parathyroid hormone (PTH).

• ↓ 1,25 Dihydroxy vitamin D
• Normal urinary cAMP
• ↓ Urinary phosphate

• Genetic defect causing end organ resistance to the action of parathyroid hormone (PTH).
• Combination of inactivating mutations of GNAS1 and Albright’s osteodystrophy

• There is deficiency of parathyroid hormone in hypoparathyroidism.
• Deficiency of parathyroid hormone causes body to decrease:
  • Reabsorption of calcium from bone.
  • Excretion of phosphate.
  • Reabsorbtion of calcium from distal tubules.
  • Vitamin D mediated absorption of calcium from intestine.

• ↓ 1,25 Dihydroxy vitamin D
• Normal urinary cAMP
• Normal urinary phosphate

• Decreased parathyroid hormone (PTH) secretion
• Skeletal resistance to parathyroid hormone (PTH)

• ↓ serum magnesium
• ↓/Normal serum potassium

• Genetic defect causing end organ resistance to the action of parathyroid hormone (PTH)
• PRKAR1A germ-line mutation in the encoding gene resulting in parathyroid resistance

• Genetic defect causing end organ resistance to the action of parathyroid hormone (PTH)
• Phosphodiesterase 4D (PDE4D) gene mutation resulting in parathyroid resistance

• Genetic defectcausing end organ resistance to the action of parathyroid hormone (PTH)
• Homozygous or heterozygous mutations in both alleles encoding the type 1 parathyroid hormone receptor resulting in parathyroid resistance

• Increase in secretion of parathyroid hormone (PTH) from a primary process in parathyroid gland.
• Parathyroid hormone causes increase in serum calcium.

• Increase in secretion of parathyroid hormone (PTH) from a secondary process.
• Parathyroid hormone causes increase in serum calcium after long periods.

• Continuous elevation of parathyroid hormone(PTH) even after successful treatment of the secondary cause of elevated parathyroid hormone.
• Parathyroid hormone causes increase in serum calcium.

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