Forteo Safely Treats 4-Month-Old With Severe Hypoparathyroidism
Six months of treatment with Forteo (teriparatide) — a lab-made parathyroid hormone fragment approved for osteoporosis — safely led to calcium and phosphate control in a 4-month old girl with severe hypoparathyroidism, a case report found.
These findings highlight the potential of this off-label medication to treat infants with hypoparathyroidism who fail to respond to standard therapy. However, additional studies are required of the treatment’s long-term safety and efficacy for pediatric patients, the investigators noted.
The case report “Teriparatide Therapy in a 4-Month-Old With Severe Hypoparathyroidism” was published in the Journal of Pediatric Pharmacology and Therapeutics.
Hypoparathyroidism is characterized by abnormally low levels of the parathyroid hormone (PTH), which leads to low calcium levels (a condition called hypocalcemia), high levels of phosphate in the blood, and a shortage of vitamin D, which helps the body absorb calcium.
Standard treatment typically includes oral calcium and vitamin D supplements. Dietary changes, including calcium-rich foods while avoiding foods rich in phosphorus, are usually also employed.
Forteo, developed by Eli Lilly, is a lab-made fragment of the active region of PTH approved to treat adults with osteoporosis, a condition that causes bones to become weak and brittle. It is administered by subcutaneous (under-the-skin) injections or through a pump system.
Although Forteo has been suggested as a PTH replacement therapy for hypoparathyroidism, its use for pediatric patients is limited due to a lack of studies assessing its long-term safety and efficacy.
A team at Shawn Jenkins Children’s Hospital in Charleston, South Carolina, describe the case of a 4-month-old girl, born prematurely at 32 weeks of gestation with several anomalies.
She was diagnosed with atypical complete DiGeorge syndrome, a rare genetic disease characterized by the absence or underdevelopment of a functioning thymus, the gland specialized in the production of immune T-cells, and severe hypoparathyroidism. She was in need of a thymus transplant.
The baby was prescribed with cholecalciferol (also known as vitamin D3) and calcitriol (the active form of vitamin D), as well as calcium carbonate. However, her phosphorus levels remained abnormal, as did her PTH levels.
After consultation with her pediatric nephrologist — one of her kidneys had failed to develop — Forteo was considered. A dose was settled on after checking the literature, specifically a case report where Forteo was administered by subcutaneous injection twice daily to a 4-year-old with hypocalcemia.
The baby was started on Forteo at a dose of 2 micrograms (mcg) given as subcutaneous injections twice daily (morning and evening).
Before then, she began tube-feeding with EleCare, a special amino acid-based hypoallergenic infant formula for medical use. Due to the baby’s high levels of phosphorus, sevelamer, a phosphate binder treatment, was also given.
Sevelamer was stopped a day after starting Forteo, as her phosphorus levels were declining.
Throughout her treatment, the use of calcium carbonate, Forteo, and calcitriol were adjusted to maintain blood calcium above 1 millimole per liter (mmol/L) without exceeding the upper normal level for total calcium.
With blood calcium levels remaining low, Forteo’s dose was increased to 2.4 mcg twice daily at day 14, then to 3.2 mcg by day 18, and to 3.9 mcg twice daily on day 28.
Treatment was maintained at this dose for two months, after which it was increased to 4.8 mcg and then 5.6 mcg twice daily a week later. Blood tests showed her calcium levels remained low.
Still, “only 7 IV calcium gluconate doses were required during the 6 months of therapy, which was a substantial decrease compared with her requirements prior to starting therapy,” the investigators wrote.
Within five months, Forteo was reduced to 4.8 mcg twice-daily dose, with calcium levels now above 1.3 mmol/L. Forteo was well-tolerated, with no evidence of hypercalcemia (abnormally high calcium levels).
During the treatment period, the baby’s blood levels of PTH remained undetectable.
The investigators concluded that teriparatide proved to be “safe and effective for our patient” throughout its six months of use.
“Teriparatide therapy can be a potential option for patients with hypoparathyroidism refractory [unresponsive] to conventional management,” the scientists wrote.
Still, “larger studies are needed to demonstrate long-term safety and efficacy of teriparatide use in pediatrics,” they added. “One of the limiting steps to teriparatide therapy in the pediatric population is the ability to safely measure and administer a smaller dose than what is commercially available.”