Screening for parathyroid hormone resistance in patients with nonphenotypically evident pseudohypoparathyroidism.
OBJECTIVE
Hypocalcemia and hyperphosphatemia in the setting of elevated parathyroid hormone (PTH) and normal vitamin D metabolites, raises the possibility of PTH resistance. The idiopathic and inherited forms of PTH resistance are referred to as pseudohypoparathyroidism. Nonphenotypically evident pseudohypoparathyroidism can go undiagnosed for decades. We have designed a new test to diagnose PTH resistance and confirmed its clinical utility in the diagnosis of pseudohypoparathyroidism.


METHODS
Our test consists of a subcutaneous injection of commercially available recombinant PTH and concomitant measurement of cyclic adenosine monophosphate in urine. We implemented the test in 2 patients with recalcitrant hypocalcemia and a healthy control subject.


RESULTS
Our test unequivocally demonstrated PTH resistance in both patients. One of the patients had phenotypically evident pseudohypoparathyroidism type-1a hence, PTH resistance was suspected. The other patient with nonphenotypically evident disease, also showed PTH resistance and was later demonstrated to have pseudohypoparathyroidism type-1b at the genomic level and confirmed to be of familial type.


CONCLUSIONS
Our results show for the first time the implementation of a simple new diagnostic tool designed to check for PTH resistance. This new test has already proven to be useful in few occasions at our institution. Larger populations, however, should be tested before implementation of such a test is considered a standard of care.
Division of Endocrinology, Diabetes and Metabolism, Department of Medicine, School of Medicine and Veterans Affairs Medical Center, University of Wisconsin-Madison, Madison, Wisconsin 53792-5148, USA.
Kristina
K
Todorova-Koteva
Kelly
K
Wood
Shahnawaz
S
Imam
Juan Carlos
JC
Jaume
D000328:Adult; D000242:Cyclic AMP / Q000652:urine; D003955:Diagnostic Tests, Routine / Q000379:methods*; D006801:Humans; D006996:Hypocalcemia / Q000652:urine; D007279:Injections, Subcutaneous; D008297:Male; D008403:Mass Screening / Q000379:methods*; D008875:Middle Aged; D010281:Parathyroid Hormone / Q000008:administration & dosage / Q000502:physiology*; D010641:Phenotype; D011547:Pseudohypoparathyroidism / Q000175:diagnosis* / Q000503:physiopathology* / Q000652:urine; D011994:Recombinant Proteins / Q000008:administration & dosage
D010281:Parathyroid Hormone; D011994:Recombinant Proteins; D000242:Cyclic AMP