Clinical heterogeneity of pseudohypoparathyroidism: from hyper- to hypocalcemia

Pseudohypoparathyroidism (PHP) is a rare inherited syndrome characterized by parathyroid hormone (PTH) resistance and is frequently associated with Albright's hereditary osteodystrophy and resistance to other cAMP-mediated hormones. The usual neonatal presentation is mild primary hypothyroidism secondary to resistance to thyroid-stimulating hormone; hypocalcemia usually develops after age 3-5 years. This work describes the diversity in the clinical expression and course of PHP, with emphasis on calcium levels by age and treatment, in 8 children under long-term follow-up at our pediatric tertiary center. The calcium levels at presentation ranged from transient neonatal hypocalcemia to infantile hypercalcemia to childhood/adolescence hypocalcemia. Interestingly, relative hypocalciuria at diagnosis and during therapy, in the presence of renal PTH resistance, was the rule. These findings indicate that transient neonatal hypocalcemia associated with other clinical features or a family history of PHP may be a flag for clinicians to screen for PTH resistance later in life. In addition, PTH resistance may be missed by surveying calcium levels only; thus the PTH levels have to be checked as well. In addition, the recommendation for patients with hypoparathyroidism that strict low-normal calcium levels be maintained during therapy in order to prevent hypercalciuria is probably not applicable in PHP.