Pseudohypoparathyroidism (PHP) is a rare inherited disorder characterized by target organ resistance or unresponsiveness to parathyroid hormone (PTH). The syndrome mimics hypoparathyroidism with patients experiencing hypocalcemia and hyperphosphatemia. However, instead of having low PTH levels, elevated levels of PTH are present in serum. PHP is typically classified as either type 1 or type 2, and then type 1 is further subdivided into 1a, 1b, or 1c. Type 1 is distinguishable from type 2 by the abnormal cAMP response to G protein activation seen in type 1, whereas the cAMP response is normal in type 2. PHP 1a and 1c both can exhibit multi-hormone resistance, whereas 1b is localized only to the kidney. Of all the subtypes of PHP, type 1a is thought to be the most common subtype, but PHP type 1b has recently been found to occur with similar frequency.
Copyright © 2024, StatPearls Publishing LLC.