July - September 2008, Volume 4, Issue 3

Trifanescu RA, Alexiu F, Dumitrascu A, Coculescu M

Type Ib pseudohypoparathyroidism associated with thrombocytopenia and possibly resistance to TSH

Acta Endo (Buc) 2008, 4 (3): 321-335
doi: 10.4183/aeb.2008.321

An 18 years old, tall man presented for circumoral numbness, paresthesias, and hypocalcaemia, without carpopedal spasm or seizures. Previous medical history revealed bilateral cataract and osseous cysts on limbs at the age of 12. Hypocalcaemia resistant to calcium treatment and mild increased TSH levels were present. At diagnosis, we noticed a normal phenotype with tall stature, moderate hypocalcaemia (5.8 mg/dL), hyperphosphatemia (5.08 mg/dL) and significantly higher than normal intact parathormone (PTH) levels (518 pg/mL), in the presence of normal serum levels of 25-hydroxy vitamin D (53.56 ng/mL). The mother and the family members have been found in good health. All these data strongly suggested sporadic pseudohypoparathyroidism type Ib (PHP-Ib), but with some features of PHP - type Ia, like the osseous cysts. We were not able to perform molecular genetic tests. The nearly complete recovery of clinical and biochemical signs (normalization of PTH, calcaemia, phosphatemia, and a normal DXA osteodensitometry) after 2 years of chronic treatment with activated 1,25- dihydroxycholecalciferol (2.00-0.75 μg/day) indirectly, but strongly confirmed the diagnosis of pseudohypoparathyroidism. The patient may have resistance to TSH evidenced by high TSH\r\n(range 4.8-7.5 mIU/L), with normal thyroid hormone levels, absence of goiter and normal TPO antibodies. The TRH test (400 μg i.v.) showed a response of TSH, and also of serum thyroxine and triiodothyronine in a range that did not clarify the diagnosis. This association of the resistance to TSH with type Ib PHP was relatively recently reported by two groups (17,20) and before them it was reported only in PHP-Ia. Our patient also showed mild thrombocytopenia, with normal bleeding time, indicating also a possible Gsα deficiency in platelets. In conclusion, our patient with sporadic pseudohypoparathyroidism without clinical phenotype of Albright hereditary osteodystrophy is highly suggestive for the type Ib PHP. A possible resistance to TSH and thrombocytopenia associated are features related to the genetic mechanisms found also in type Ia PHP. It is tempting to suggest that this case is one of the new variants of pseudohypoparathyroidism-Ib, recently reported.

Keywords: pseudohypoparathyroidism type Ib, pseudohypoparathyroidism type Ia, resistance to TSH, hypocalcaemia

Correspondence: Mihail Coculescu, MD, Department of Endocrinology, “Carol Davila” University of Medicine and Pharmacy, 34-36 Aviatorilor Blvd, 011863 Bucharest, Romania, e-mail: m.coculescu@uni-davila.ro