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pseudohypoparathyroidism
Congenital & hereditary disorder of PTH resistance.
Etiology: resistance to PTH (generally partial resistance)
Pathology:
1) parathyroid hyperplasia
2) diminished urinary cAMP response to PTH
Genetics:
1) X-linked form
2) autosomal form
3) defective allele for Gs-alpha, GNAS (type 1A)
4) defects in methylation of GNAS/GNAS1 gene; normal activity of the product of GNAS (type 1B)
Clinical manifestations:
1) symptoms of hypothyroidism
2) developmental & skeletal abnormalities
3) most patients show characteristic phenotype of Albright's hereditary osteodystrophy (also involves GNAS)
4) type 1B lacks developmental defects characteristic of Albright's hereditary osteodystrophy
Laboratory:
1) serum PTH: elevated
2) serum magnesium: hypomagnesemia
3) serum calcium: diminished
4) serum phosphate: elevated
5) serum 25-OH vitamin D: low (vitamin D deficiency)
5) renal function tests (chronic renal failure)
Management:
-> treat as hypoparathyroidism except that the doses of vitamin D & calcium are usually lower than those with true hypopara-thyroidism
Related
Albright's hereditary osteodystrophy (AHO)
Gs-alpha
hyperparathyroidism
hypomagnesemia
hypoparathyroidism
Specific
pseudohypoparathyroidism type 1B (PHP1B)
General
endocrine disease
developmental disorder
Database Correlations
OMIM correlations
References
- Medical Knowledge Self Assessment Program (MKSAP) 11, American
College of Physicians, Philadelphia 1998
- Harrison's Principles of Internal Medicine, 14th ed.
Fauci et al (eds), McGraw-Hill Inc. NY, 1998, pg 2244-45
- Harrison's Principles of Internal Medicine, 13th ed.
Isselbacher et al (eds), McGraw-Hill Inc. NY, 1994, pg 1258