Continuous Forsteo Effective for Case of Severe Hypoparathyroidism

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by Vanda Pinto, PhD |

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In a woman whose severe hypoparathyroidism did not respond to standard treatment, constant infusion of a lab-engineered form of the parathyroid hormone (PTH) eliminated symptoms and improved her quality of life, a case study from Portugal reports.

This medication, called Forsteo (teriparatide) and marketed in the U.S. as Forteo, is an approved therapy for osteoporosis, a condition that causes bones to become weak and brittle.

The study, “Continuous Teriparatide Treatment in Chronic Hypoparathyroidism: A Case Report,” was published in the American Journal of Case Reports.

Hypoparathyroidism is characterized by low levels of PTH, which leads to calcium deficiency, or hypocalcemia, and hyperphosphatemia (high levels of phosphorus) in the blood. Symptoms of hypocalcemia include numbness, severe muscle pain, and involuntary muscle contractions.

Standard treatment for hypoparathyroidism consists of calcium and vitamin D replacement. Vitamin D helps the body absorb calcium. However, for some patients, symptoms still persist even with supplementation.

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Recently, researchers have steered their focus on developing a way to replace the missing hormone. Eli Lilly’s Forsteo is a lab-made fragment of PTH that can be delivered by subcutaneous (under-the-skin) injections or through a pump system. Studies have shown it could normalize the levels of calcium, a main component of bone.

Since the long-term effects of replacement therapy are still unknown, this form of treatment is not generally recommended in Europe. However, Forsteo has been shown to be effective for treating chronic hypoparathyroidism both with under-the-skin injections and pump delivery systems.

The study described the case of a 31-year-old woman who was referred to the endocrinology department at Porto University Hospital Center, in Portugal, for evaluation and treatment of chronic severe hypocalcemia. She had developed hypoparathyroidism after her parathyroid glands had been removed during surgery for thyroid cancer. A thyroidectomy — surgery to remove the thyroid — can cause hypoparathyroidism when the parathyroid glands, which produce PTH, are accidentally removed or damaged.

The patient’s therapy regimen for hypoparathyroidism consisted of multiple daily doses of calcium, vitamin D, magnesium, indapamide — a diuretic that helps to reduce calcium lost through the urine — and Forsteo injections, at a dose of 20 micrograms (mcg), three times a day.

Yet, she continued to experience daily muscle spasms, cramps, numbness, and tingling sensations in the area around her mouth and in her fingers. Because of the severity of these symptoms, the woman was often admitted to the emergency room where she would receive intravenous (into-the-vein) calcium perfusions. Due to the frequency of the episodes, a long-term central venous catheter was placed in her chest for calcium administration.

While she was hospitalized, oral calcium, vitamin D3, and alphacalcidol (a vitamin D3 derivative) were maintained, and doses were increased up to 5 grams/day of calcium and 4 mcg/day of alphacalcidol. However, the patient still had six subsequent episodes of severe hypocalcemia.

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In an effort to manage her hypoparathyroidism episodes, the team decided to use a constant perfusion of Forsteo, through a Roche insulin pump. On the first day, the medical team started the perfusion at a rate of 0.2 international units per hour (IU/h) or 12 mcg of teriparatide/day, and continued with the previous doses of calcium and vitamin D.

The next day, the patient had an episode of severe hypocalcemia, so the infusion rate was increased slowly up to 0.5 IU/h (30 mcg of teriparatide/day). The dose of oral calcium was then reduced to 4 grams/day. During the rest of her hospital stay, no other severe hypocalcemia episodes were reported. Calcium levels increased in her blood and decreased in the urine. Blood phosphate also gradually decreased.

Two months after leaving the hospital, the patient’s infusion rate was still at 0.5 IU/h, and she was taking less calcium (1 g/day ) and vitamin D (0.25 mcg/day). After four months, calcium and vitamin D supplementation were no longer needed, and her blood calcium levels continued to be within a normal range.

No other adjustments to the perfusion rate were needed thereafter. The patient also had learned to operate the pump on her own and reported a much better quality of life.

“To our knowledge, this case represents one of the very few reports of successful treatment of hypoparathyroidism with a continuous perfusion of PTH, shedding a light on this novel treatment for severe cases of chronic hypoparathyroidism,” the researchers concluded.