Effects of supplemental vitamin D on muscle performance and quality of life in Graves' disease: a randomized clinical trial

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Background Vitamin D deficiency has been proposed a role in development and course of Graves' disease (GD). Muscle weakness and quality of life (QoL) impairments are shared features of GD and vitamin D deficiency. We aimed to investigate whether vitamin D supplementation would improve restoration of muscle performance and thyroid-related QoL in GD and to describe the effect of anti-thyroid medication (ATD) on these outcomes. Methods. In a double-blinded clinical trial, hyperthyroid patients with a first time diagnosis of GD were randomized to vitamin D 70 mcg (2800 IU)/day or matching placebo as add-on to standard ATD. At baseline and after three and nine months of intervention, we assessed isometric muscle strength, muscle function tests, postural stability, body composition, and QoL-impairment using ThyPRO. Linear mixed modelling was used to analyze between-group differences in change and the effects of ATD. (The DAGMAR study clinicaltrials.gov ID NCT02384668). Results. Nine months of vitamin D supplementation caused an attenuation of muscle strength increment in all muscle groups investigated, significant at knee extension 60° where the increase was 24% smaller (p=0.04) in the vitamin D group compared with placebo. Compared to placebo, vitamin D supplementation tended to reduce gain of lean body mass (-24%, p=0.08). Vitamin D supplementation significantly impeded alleviation of Composite QoL and the same tendency was observed for the Overall QoL-Impact and Impaired Daily Life scales. In response to ATD, all measures improved significantly. The increase in muscle strength ranged from 25-40% (Pall < 0.001) and increment of lean body mass was 10% (p<0.001). Large changes were observed in all QoL scales. Conclusion Nine months of vitamin D supplementation 70 mcg/day caused unfavorable effects on restoration of muscle performance. In contrast, ATD treatment was associated with marked improvement in all measures of muscle performance and thyroid-related QoL. In patients with newly diagnosed GD, high dose vitamin D supplementation should not be recommended to improve muscle function, but ATD is of major importance to alleviate muscle impairment.

TidsskriftThyroid : official journal of the American Thyroid Association
Sider (fra-til)661-671
StatusUdgivet - maj 2020

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