Clinical feature: 

Definition: Pseudohypoparathyroidism is characterized by elevated plasma levels of PTH and symptoms consistent with reduced PTH levels - hence a resistance of peripheral organs to PTH.

Diagnostics: 

Differential: Type 1 is cause by mutation or impaired imprinting of GNAS1 gene. In contrast to type 2 the renal cAMP excretion in response to PTH administration is blunted. Type 2 is not yet characterized genetically.
   The genetic background of type 2 pseudohypoparathyroidism is not yet characterized. Moreover, severe vitamin D deficiency resembles pseudohypoparathyroidism with normal renal cAMP response to PTH, so an acquired disease or a hereditary disease in vitamin D metabolism have to be ruled out prior to searching a gene responsible for pseudohypoparathyroidism type 2.
   Type 1 is further branched into types 1a, 1b, 1c. Type 1a is equivalent to Albright hereditary osteodystrophy, type 1b has not skeletal abnormalities, and in type 1c the protein shows normal activity in erythrocytes.

Literature: 

Rao DS et al. (1985) Dissociation between the effects of endogenous parathyroid hormone on adenosine 3',5'-monophosphate generation and phosphate reabsorption in hypocalcemia due to vitamin D depletion: an acquired disorder resembling pseudohypoparathyroidism type II.
Drezner M et al. (1973) Pseudohypoparathyroidism type II: a possible defect in the reception of the cyclic AMP signal.
Linglart A et al. (2002) GNAS1 lesions in pseudohypoparathyroidism Ia and Ic: genotype phenotype relationship and evidence of the maternal transmission of the hormonal resistance.