Endocrine Abstracts

Introduction: Whether patients with non-surgical hypoparathyroidism have skeletal muscle dysfunction is not studied. It is also not known if skeletal muscle dysfunction involves respiratory muscles and results in a restrictive lung disease (RLD).

Aim: To assess skeletal muscle and pulmonary function in patients with non-surgical hypoparathyroidism, who were asymptomatic for overt muscle and lung diseases.

Methods: Thirty patients with non-surgical hypoparathyroidism (mean age 37.7 years, 60% males) and forty healthy-controls were assessed for skeletal muscle function by hand-grip strength, short physical performance battery (SPPB) test, dual-energy x-ray absorptiometry, and electromyography. Pulmonary function was assessed in all by spirometry and diaphragmatic ultrasound. Those with a restrictive pattern on spirometry further underwent body plethysmography and diffusion lung capacity for carbon monoxide to confirm presence of RLD.

Results : Patients with hypoparathyroidism had lower levels of serum calcium (2.25±0.15 vs 2.4±0.12 mmol/l, P<0.001), magnesium [median (interquartile-range) 0.74 (0.69-0.82) vs 0.78 (0.69-0.90) mmol/l, P=0.04], hand-grip strength (18.08±8.36 vs 22.90±7.77 kg, P=0.01) and SPPB score (9.5 [7-10] vs 12 [12-12], P<0.001) compared to healthy-controls. Electromyographic evidence of myopathy was seen in 23% (5 of 22) patients with hypoparathyroidism, but none of the controls (P=0.08). The proportion of patients with a RLD was higher in the group with hypoparathyroidism compared with controls (21% vs 0%, P=0.01). Diaphragmatic excursion (4.22±1.38 vs 5.18±1.53 cm, P=0.01) and thickness (3.79±1.18 vs 4.28±0.94 mm, P=0.05) on deep inspiration were reduced in patients with hypoparathyroidism. Lean body mass was comparable in both the groups. In the multivariable analysis, the average of measurements of serum calcium in the previous year predicted hand-grip strength and SPPB score in patients with hypoparathyroidism.

Conclusion: Detailed testing of patients with hypoparathyroidism who were asymptomatic for overt muscle and lung diseases revealed significant impairment in parameters of skeletal muscle function. A substantial proportion of patients with hypoparathyroidism had electromyographic evidence of myopathy and RLD.