Parathyroid Hormone for Hypoparathyroidism May Be Effective Over Long Term

SEATTLE — Human parathyroid hormone (PTH [1-84]) appears to be a safe and effective long-term treatment option for hypoparathyroidism, according to results from a new 7-year study.

Additionally, the data indicate that a course of continuous PTH (1-84) treatment was associated with significant reductions in calcium supplementation and calcitriol supplementation.

“It helps to raise parathyroid hormone levels in the blood and thus increases serum calcium absorption through the intestine, resorption from the bone, and resorption in the kidney,” said study investigator Mishaela Rubin, MD, who is an associate professor of clinical medicine at Columbia University in New York.

Dr Rubin, who presented the study findings at the American Society for Bone and Mineral Research (ASBMR) 2015 Annual Meeting, said this study represents the longest experience with the therapeutic use of parathyroid hormone (PTH) for any condition.

These findings also demonstrate the efficacy and safety of PTH (1-84) as an effective long-term option for patients with hypoparathyroidism, she added.

Hypoparathyroidism often leads to hypocalcemia, hyperphosphatemia, and hypercalciuria. Moreover, these patients often have above average bone mineral density (BMD). Previously, Dr Rubin and colleagues demonstrated that 6 years of treatment with PTH (1-84) treatment improved these conditions. Because hypoparathyroidism is a lifelong condition, however, it is imperative that studies look at the long-term risks and benefits of this therapy, she noted.

The investigators evaluated 21 patients with hypoparathyroidism (mean age, 46.5 years). Mean duration of disease was 19.3 years, and 14 of the 21 patients were female. 

The etiologies were listed as postsurgical in 11 patients and as autoimmune in 9 patients. The baseline medications included calcium, calcitriol, vitamin D, and hydrochlorothiazide (HCTZ). At baseline, mean serum calcium was 8.5 mg/dL, PTH levels were undetectable, and serum phosphate was 4.4 mg/dL. The investigators also measured BMD.

All patients at baseline received 100 mcg of PTH (1-84) every other day. However, after 3 years of treatment, patients were switched to doses that ranged from 25 mcg to 100 mcg per day.

After 7 years of continuous therapy, calcium supplementation decreased by 60% (P=.0001) and calcitriol by 56% (P=.006), according to the study results.

Vitamin D intake and HCTZ dose remained the same throughout the study period, reported Dr Rubin.

Results also indicated that serum calcium remained stable and 24-hour urinary calcium decreased by 32%.

Elevation of serum calcium above the upper limit of normal was only reported in 5% of all measurements.

No changes in serum phosphate, magnesium, or creatinine were observed, though the investigators noted increases in total alkaline phosphatase and BMD at the lumbar spine and total hip.

One kidney stone and 3 minor fractures reported.

In light of these results, the investigators concluded that this treatment regimen is able to maintain normal calcium metabolism with continuous therapy.

“We have separate published data that also show it helps with quality of life,” Dr Rubin said in an interview with Endocrinology Advisor. “But this is the longest study of its kind, and it is important because it shows that in patients who have hypoparathyroidism that this drug can work for as long as 7 years to allow them to take less calcium and calcitriol supplementation.”

Reference

1. Rubin M. Abstract FR0018: PTH(1-84) Treatment is Safe and Effective in Hypoparathyroidism for Seven Years. Presented at: American Society for Bone and Mineral Research (ASBMR) 2015 Annual Meeting; Oct. 9-12, 2015; Seattle.