Complications of HPT

Rates of complications, including renal disease, are high in patients with hypoparathyroidism, new data reveal.

Hypoparathyroidism is a rare disorder characterised by hypocalcaemia together with low or inappropriately normal levels of parathyroid hormone (PTH). A common cause of hypoparathyroidism is damage or removal of the parathyroid glands during thyroidectomy; other causes include parathyroid autoimmunity and complex genetic syndromes. Most patients with the disorder receive calcium supplements and vitamin D analogs. However, the treatment does not directly replace the action of PTH; therefore, complications can occur. Mitchell et al. conducted a large, longitudinal cohort study to determine the rates of complications in 120 patients (73% female) with permanent hypoparathyroidism who were identified from a patient data registry and followed up for a mean of 7.4 years.

“Questions we hoped to address included: what are the prevalences of kidney stones, nephrocalcinosis, and chronic renal disease? How often are patients hypocalcaemic or hypercalcaemic? What is the relationship between serum calcium and renal and other complications over time?,” explains senior author Michael Mannstadt of Massachusetts General Hospital.

Serum calcium levels were maintained within a calcium range of 1.9–2.4 mmol/l for an average of 86% of the time in the patients. Nevertheless, 24 h urine measurements of calcium in 53 patients showed that 38% had at least one measurement indicating an episode of frank hypercalciuria (>300 mg per day). Renal imaging in 54 patients indicated renal calcifications in 31% of this group. Rates of chronic renal failure were significantly higher than age-matched norms from the National Health and Nutrition Examination Survey 1999–2006.

“Our study shows that hypoparathyroidism is not at all a benign disease,” points out Mannstadt. “Monitoring urinary calcium excretion and adjusting treatment to lower it is a critical part of medical management. However, no clinical guidelines are available for the management of the disease, a gap that will hopefully be filled in the near future.”