Bone Abstracts

PTH replacement therapy in hypoparathyroidism (hypoPT) has become more accepted after proving successful in several clinical studies. Intact PTH (PTH_1–84) was in 2012 withdrawn, leaving teriparatide (PTH_1–34) the only therapeutic option available.

All patients with postoperative HypoPT who changed medication from PTH_1–84 (100 μg) to PTH_1–34 (20 μg), after at least 12 months of conventional therapy and a minimum of 6 months of PTH_1–84 were included. The following treatment with PTH_1–34 was for at least 3 months. Plasma ionized calcium, daily dose of 1α-hydroxylated-vitamin D metabolites (Etalpha), calcium and PTH was collected.

Eight patients (women=88%) with a mean age of 54±12 years and a duration of hypoPT of 13±6 years were included. Before initiation of PTH_1-84 the mean daily dose of Etalpha was 1.9±1.1 μg and calcium supplements were 1550±705 mg. Etalpha dose was reduced with 86±35% (P=0.01) after 6 months of PTH_1–84 treatment and terminated in seven patients. Calcium were reduced with 78±36% (P=0.02) to 273±353 mg and stopped in four patients. Six patients received 100 μg PTH_1–84 a day, the seventh received PTH 2 out of 3 days and the last one received PTH_1–84 every other day.

When changing from PTH_1–84 to PTH_1–34, plasma ionized calcium initially dropped and the demand for supplements increased. Etalpha was resumed in four patients; mean daily dose increased to 0.99±1.26 μg (P=0.04) and calcium increased to 329±368 mg (P=0.72). Five patients received 20 μg PTH_1-34 a day; two patients twice a day and one 20/40 μg alternately.

Compared with PTH_1–34, PTH_1–84 has a longer plasma half-life and a higher calcemic response. We have shown a need for higher doses of Etalpha and calcium supplements to maintain normal serum calcium when treated with PTH_1–34 compared to PTH_1–84 and in some a need for more than one daily dose.