Due to acciental surgical excision of parathyroid glands, autoimmune destruction, or DiGeorge syndrome.

Findings: tetany, hypocalcemia, hyperphosphatemia.- Chvostek sign – tapping of facial nerve → contraction of facial muscles- Trousseau sign – occlusion of brachial artery with BP cuff → carpal spasm

Pseudohypoparathyroidism type 1A – unresponsiveness of kidney to PTH → hypocalcemia despite ↑ PTH levels. Presents as a constellation of physical findings known as Albright hereditary osteodystrophy: shortened 4th/5th digits, short stature, obesity, developmental delay. Autosomal dominant. Due to defective G_s protein α-subunit causing end-organ resistance to PTH. Defect must be inherited from mother due to imprinting.Pseudopseudohypoparathyroidism – physical exam features of Albright hereditary osteodystrophy but without end-organ PTH resistance (PTH level normal). Occurs when defective G_s protein α-subunit is inherited from father.