Clinical calcium
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Pseudohypoparathyroidism type I b is characterized by unresponsiveness solely to parathyroid hormone in contrast to pseudohypoparathyroidism type I a which induces resistance to several hormones. Abnormal imprinting of GNAS gene which encodes Gsalpha protein is considered to be responsible for pseudohypoparathyroidism type Ib. ⋯ However, the detailed mechanism how these deletions cause abnormal imprinting of GNAS gene remains to be elucidated. Analysis of pathogenesis of pseudohypoparathyroidism type Ib should contribute to the understanding of regulatory mechanisms of gene expression.
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Pseudophypoparathyroidism (PHP) is characterized by hypocalcemia, hyperphosphatemia and elevated levels of parathyroid hormone (PTH) due to resistance to PTH. PHP type I a is caused by heterozygous inactivating mutation of the GNAS1 gene, which encodes signal transducer, Gsalpha. PHP type I a is associated with Albright's osteodystrophy (AHO). Those patients who have AHO phenotype without hormone resistance are affected by pseudopseudohypoparathyroidism.