Table 2.

Clinical, Biochemical, and Genetic Features of Hypoparathyroid and Pseudohypoparathyroid Disorders

	Hypoparathyroidism	PHP
		PHP1A	PPHP	PHP1B	PHP1C	PHP2
AHO manifestations	No	Yes	Yes	No/rarely	Yes	No
Serum calcium	↓	↓	N	↓	↓	↓
Serum PO4	↑	↑	N	↑	↑	↑
Serum PTH	↓	↑	N	↑	↑	↑
Response to PTH
Urinary cAMPa (Chase-Aurbach test)	↑	↓	↑	↓	↓	↑
Urinary PO4 (Ellsworth-Howard test)	↑	↓	↑	↓	↓	↓
Gsα activity	N	↓	↓	N	N	N
Inheritance	AD/AR/X	AD	AD	AD/sporadic	AD	Sporadic
Molecular defect	PTH/CaSR/GATA3/GCM2/others	GNAS	GNAS	STX16/GNASb	GNAS	? cAMP targets
Other hormonal resistance	No	Yes	No	In some patients	Yes	No

Abbreviations: ↓, decreased; ↑, increased; N, normal; AD, autosomal dominant; AR, autosomal recessive; X, X-linked, AHO, Albright's hereditary osteodystrophy presumed, but not proven.

^aPlasma cAMP responses are similar to those of urinary cAMP.

^bInvolves deletions that are located upstream of GNAS.

[Adapted from R. V. Thakker: The parathyroid glands, hypercalcemia, and hypocalcemia. In: Goldman L, Shafer AI, eds. Goldman-Cecil Medicine. 25th ed. Atlanta, GA: Elsevier Ltd; 2016:1649–1661 (67), with permission.]