Endocrine Abstracts

Introduction: Hypoparathyroidism can occur post-surgically after thyroid or parathyroid surgery or in autoimmune or genetic diseases. Over several decades, the management of hypoparathyroidism included only supplementation with calcium, vitamin D3 (cholecaliferol), as well as active 1,25-dihydroxyvitamin D (calcitriol). In cases with severe hypoparathyroidism, this treatment can be limited by hypercalciuria, and these patients often need substitution with recombinant parathyroid hormone. In daily clinical practice, thiazide diuretics may also be administered to reduce calciuria, however few data are available on the effects of thiazide use in hypoparathyroidism.

Methods: In this observational study, we retrospectively analyzed patients with hypoparathyroidism in routine medical treatment at our endocrine outpatient clinic. Clinical and biochemical parameters were collected at the time of first presentation, before the initiation of thiazide treatment, and at the time of last check-up.

Results: Our cohort includes 103 patients (m/f n=21/82) with hypoparathyroidism who were observed for a median of 2.1 (± 6.6) years. 81 of those patients had prior thyroid or parathyroid surgery (26 due to thyroid nodules, 14 due to thyroid cancer, 17 due to Graves’ disease, 4 due to primary hyperparathyroidism and 2 due to primary hyperparathyroidism and thyroid nodules), while hypoparathyroidism was not surgery-related in 19 patients.A therapy with thiazide diuretics (hydrochlorothiazide with a median dose of 12.5 mg±12.5 mg) was established in 40 of those patients. During treatment with thiazides, while parathyroid hormone measurements significantly decreased (7.9 to 4.8 pg/ml, P=0.011), albumin-adjusted serum calcium (2.0 and 2.1 mmol/l, respectively), estimated glomerular filtration rate (81.6 and 77.5 ml/min/1.73 m²), magnesium (0.79 and 0.78 mmol/l) and blood pressure levels (135/85 and 134/84 mmHg) remained stable. Calciuria significantly decreased (9.5 to 6.2 mmol/24 h, P=0.018) and calcium and calcitriol dosages were non-significantly reduced.

Conclusion: Out data show that thiazide diuretics significantly lower calciuria in patients with hypoparathyroidism, but they do not impact serum calcium, magnesium, eGFR or blood pressure levels.