Forsteo May Be Safe Tool to Control Calcium, Phosphate in Children

Marta Figueiredo, PhD avatar

by Marta Figueiredo, PhD |

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Twice-daily treatment with Forsteo (teriparatide) — a synthetic parathyroid hormone fragment sold as Forteo in the U.S. — safely and significantly improves calcium and phosphate control in children with hypoparathyroidism who failed to respond to standard treatment, a small study in France shows.

During treatment of at least one year, kidney function remained stable in these children, who also reported improvements in quality of life.

These findings highlight the therapeutic potential of this off-label medication for children with hypoparathyroidism who cannot manage their disease with standard therapy. Still, larger international studies are needed to evaluate the treatment’s long-term effects, especially in terms of adverse events and quality of life, the researchers noted.

The study, “Intermittent Bi-Daily Sub-cutaneous Teriparatide Administration in Children With Hypoparathyroidism: A Single-Center Experience,” was published in the journal Frontiers in Pediatrics.

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Hypoparathyroidism is characterized by abnormally low levels of the parathyroid hormone (PTH), which results in low levels of calcium and high levels of phosphate in the blood, as well as a deficiency in vitamin D, which helps the body absorb calcium.

Chronic hypoparathyroidism is also associated with the buildup of calcium deposits in blood vessels, the brain, and the kidneys, potentially causing damage and impairing their function.

Standard treatment typically consists of calcium and vitamin D supplements, as well as active vitamin D, but patients may still experience calcium fluctuations and excessive calcium loss in the urine — called hypercalciuria — which increases the risk of chronic kidney disease.

Forsteo, developed by Eli Lilly, is an engineered fragment of PTH, specifically its active region, approved for adults with osteoporosis, a condition that causes bones to become weak and brittle.

Administered through under-the-skin injections or a continuous pump system, Forsteo has been suggested as a PTH replacement therapy for hypoparathyroidism. While several previous studies have reported its safety and effectiveness in adults who cannot control the condition with standard therapy, there has been limited evidence of its use in pediatric patients.

Now, a team of researchers in France retrospectively analyzed the data of 10 children (six boys and four girls) with hypoparathyroidism who started Forsteo at their hospital between April 2016 and June 2019 due to failure to respond to conventional therapy. All had at least one year of follow-up.

The median age of the children when they started Forsteo was 10.7 years (range of 4.1–15.5 years), and they were followed for a median of 2.8 years. Forsteo was administered twice daily at a dose of 20 micrograms, with further adjustment depending on calcium levels. All children received intermittent vitamin D (cholecalciferol) supplementation.

Six children already had calcium deposits in their kidneys.

Results showed that Forsteo significantly increased calcium levels, which remained stable within the lower normal range or just below it, and significantly reduced phosphate levels in these children.

Five of them required the reintroduction of low doses of active vitamin D, such as calcitriol, in the evening to stabilize vitamin D levels. This allowed the maintenance of Forsteo’s dose.

Kidney function and calcium levels in urine remained stable throughout the study, as well as most markers of bone metabolism. Pre-existing kidney deposits worsened in one child, and two children with no baseline kidney assessment showed moderate kidney calcium deposits during follow-up. None of the children had kidney stones.

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Severe adverse events, all related to abnormal blood calcium levels, were reported in one child. These included two episodes of low calcium levels with clinical symptoms and one episode of treatment-related higher-than-normal levels.

All three episodes were associated with a switch from continuous Forsteo treatment with a pump system, initiated at study start only in this child, to twice-daily injections after four months.

One teenager experienced loss of taste, without signs of neurological damage, which was resolved when Forsteo dosing was reduced.

While most children were non-compliant to conventional therapy before Forsteo, one still showed poor compliance with Forsteo — which was found to be related to “a very poor socio-familial support,” the researchers wrote.

In addition, most children reported an improved quality of life with Forsteo, noting that their fatigue significantly decreased with the disappearance of the muscular symptoms associated with low calcium levels.

These findings highlighted that twice-daily treatment with Forsteo “allows a better control of calcium levels, without any changes in urinary calcium, … decreases phosphate levels that may have crucial long-term consequences for improving the cardiovascular risk of these children … [and] is safe and effective with a better compliance (as compared to conventional therapy),” the scientists wrote.

While treatment guidelines propose Forsteo “as a second-line off-label therapy in these children, notably in France, larger international studies may evaluate its long-term consequences especially for the potential risk of hypercalciuria and [kidney calcium deposits] later in life,” and its effects on quality of life, the team concluded.