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Background: Hypothyroidism is common, and in iodine-sufficient areas, it is primarily caused by autoimmune destruction of the thyroid gland. Observational studies have consistently shown an inverse association between serum 25-hydroxyvitamin D concentration and autoimmune diseases; however, there is a lack of evidence from randomized controlled trials to support a benefit of vitamin D supplementation, particularly for autoimmune thyroid diseases. We, therefore, aimed to assess the effect of vitamin D supplementation on the incidence of hypothyroidism. Methods: We analyzed data from the D-Health Trial (n = 21,315), a randomized double-blind placebo-controlled trial of 60,000 international units per month of supplemental vitamin D3 among Australians aged 60 years and over. Hypothyroidism, a tertiary outcome of the D-Health Trial, was defined by treatment with levothyroxine, ascertained through linkage with the Australian Pharmaceutical Benefits Scheme. The outcome was time to first prescription of levothyroxine. We began follow-up at 12 months after randomization; people who had died or who had been dispensed levothyroxine during the first year were excluded. Flexible parametric survival models were used to assess the effect of vitamin D supplementation on hypothyroidism, overall and within strata defined by age, sex, body mass index, and predicted baseline vitamin D status. Results: We included 17,851 participants in the main analysis (vitamin D = 8939; placebo = 8912). During a median follow-up of 4.1 years (interquartile range 4.1–4.1), 293 participants developed hypothyroidism (vitamin D = 138 [1.5%]; placebo = 155 [1.7%]). Vitamin D supplementation did not significantly reduce the incidence of hypothyroidism (overall hazard ratio [HR] 0.89; 95% confidence interval [CI] 0.71–1.12). There was some suggestion of an effect in females (overall HR 0.78; CI 0.58–1.06) but not in males (overall HR 1.06; CI 0.74–1.50; p interaction 0.20). Conclusions: Vitamin D supplementation did not reduce the incidence of hypothyroidism overall; however, the possible beneficial effect observed in females warrants further investigation. Clinical Trial Registration: Australian New Zealand Clinical Trials Registry: ACTRN12613000743763. [ABSTRACT FROM AUTHOR]

Background: Vitamin D supplementation may reduce the risk or severity of infection, but this has been investigated in few large population-based trials. We analyzed data from the D-Health Trial, using prescription of antibiotics as a surrogate for infection.Methods: The D-Health Trial is a randomized, double-blind, placebo-controlled trial in which 21 315 Australians aged 60-84 years were randomized to 60 000 IU of supplementary vitamin D3 or placebo monthly for 5 years. For this analysis, the primary outcome was the number of antibiotic prescription episodes; secondary outcomes were total number of prescriptions, repeat prescription episodes, and antibiotics for urinary tract infection. We estimated incidence rate ratios (IRRs) using negative binomial regression, and odds ratios using logistic regression.Results: Vitamin D supplementation slightly reduced the number of prescription episodes (IRR, 0.98; 95% confidence interval [CI], .95-1.01), total prescriptions (IRR, 0.97; 95% CI, .93-1.00), and repeat prescription episodes (IRR, 0.96; 95% CI, .93-1.00). There was stronger evidence of benefit in people predicted to have insufficient vitamin D at baseline (prescription episodes IRR, 0.93; 95% CI, .87-.99).Conclusions: Vitamin D may reduce the number of antibiotic prescriptions, particularly in people with low vitamin D status. This supports the hypothesis that vitamin D has a clinically relevant effect on the immune system.Clinical Trials Registration: Australian New Zealand Clinical Trials Registry: ACTRN12613000743763. https://www.anzctr.org.au/. [ABSTRACT FROM AUTHOR]

Background: Falls cause considerable morbidity and mortality in older people. It is unclear how vitamin D supplementation affects falls risk, particularly when taken at high doses. We sought to determine whether monthly high‐dose vitamin D supplementation reduces risk and incidence of falls. Methods: We used data from the randomized, double‐blind, placebo‐controlled D‐Health Trial conducted in Australia. Between February 2014 and May 2015, 21 315 participants aged 60–84 years were randomized (1:1) to monthly doses of either 60 000 IU of colecalciferol or placebo for a maximum of 5 years. People who reported a history of osteomalacia, sarcoidosis, hyperparathyroidism, hypercalcaemia or kidney stones or who were taking >500 IU/day supplementary vitamin D were ineligible. Each year, we collected blood samples from ~450 randomly sampled participants from each trial arm and measured 25‐hydroxyvitamin D [25(OH)D]. Falls, a prespecified tertiary outcome, were ascertained using annual surveys and, for a subset of participants, 3‐month falls diaries. The primary outcome for this analysis was any fall in the month before completing an annual survey. As part of our process to maintain blinding, we used random samples of participants (surveys, n = 16 000; diaries, n = 2400), with equal numbers per group. Participants with no outcome data were excluded. Following an intention‐to‐treat approach, we analysed outcomes using logistic, ordinal and negative binomial regression. Registration: Australian New Zealand Clinical Trials Registry (ACTRN12613000743763); registered 4 July 2013. Results: Mean treatment duration was 4.3 years (standard deviation [SD] = 1.4 years). Mean serum 25(OH)D concentrations during the trial were 114.8 (SD 30.3) nmol/L and 77.5 (SD 25.2) nmol/L in the vitamin D and placebo groups, respectively. Survey and diary analytic sets included 15 416 and 2200 participants, respectively; approximately half were randomized to vitamin D (surveys: 50.1%; diaries: 50.4%). Vitamin D had no effect on falling in the past month (odds ratio [OR] 1.02, 95% confidence interval [CI] 0.95–1.10). There was an interaction with body mass index (BMI) (P‐interaction = 0.001); vitamin D increased risk in participants with BMI < 25 kg/m2 (OR 1.25, 95% CI 1.09–1.43), but there was no effect in those with BMI ≥ 25 kg/m2 (OR 0.95, 95% CI 0.87–1.04). Analyses of diary data were consistent with these findings. The incidence of hypercalcaemia and kidney stones did not differ between groups. Conclusions: Monthly high‐dose vitamin D supplementation did not reduce risk of falling. A possible increased risk of falling with vitamin D supplementation in people with normal BMI warrants further investigation. [ABSTRACT FROM AUTHOR]

Background: Observational data suggested that supplementation with vitamin D could reduce risk of infection, but trial data are inconsistent., Objective: We aimed to examine the effect of oral vitamin D supplementation on antibiotic use., Design: We conducted a post hoc analysis of data from pilot D-Health, which is a randomized trial carried out in a general community setting between October 2010 and February 2012. A total of 644 Australian residents aged 60-84 y were randomly assigned to receive monthly doses of a placebo (n = 214) or 30,000 (n = 215) or 60,000 (n = 215) IU oral cholecalciferol for ≤12 mo. Antibiotics prescribed during the intervention period were ascertained by linkage with pharmacy records through the national health insurance scheme (Medicare Australia)., Results: People who were randomly assigned 60,000 IU cholecalciferol had nonsignificant 28% lower risk of having antibiotics prescribed at least once than did people in the placebo group (RR: 0.72; 95% CI: 0.48, 1.07). In analyses stratified by age, in subjects aged ≥70 y, there was a significant reduction in antibiotic use in the high-dose vitamin D compared with placebo groups (RR: 0.53; 95% CI: 0.32, 0.90), whereas there was no effect in participants aged <70 y (RR: 1.07; 95% CI: 0.58, 1.97) (P-interaction = 0.1)., Conclusion: Although this study was a post hoc analysis and statistically nonsignificant, this trial lends some support to the hypothesis that supplementation with 60,000 IU vitamin D/mo is associated with lower risk of infection, particularly in older adults. The trial was registered at the Australian New Zealand Clinical Trials Registry (anzctr.org.au) as ACTRN12609001063202.

Objectives: Crohn's disease (CD; MIM 266600) is one of the most common forms of inflammatory bowel disease (IBD), and represents a significant burden to health care in developed countries. Our aim was to determine whether a gene in the IBD linkage region on chromosome 19q13, with a role in Paneth cell secretion and T-cell activation, conferred genetic susceptibility to the development of CD., Methods: In total, 792 CD cases and 1,244 controls of Australian origin (Caucasian) were genotyped for seven single-nucleotide polymorphisms (SNPs) in the gene encoding the intermediate conductance calcium-activated potassium channel protein (KCNN4) at 19q13.2. CD cases were phenotyped using the Montreal classification. The replication set comprised an additional 326 CD cases and 951 population-based Caucasian controls. Analysis of the KCNN4 mRNA transcript was carried out using quantitative reverse transcriptase-PCR., Results: KCNN4 SNP rs2306801 was associated with CD (primary P=0.0008, odds ratio (OR) (95% confidence interval (CI)): 0.76 (0.65-0.89); replication P=0.01, OR (95% CI): 0.77 (0.61-0.97). Stratification by disease location identified the association between SNP rs2306801 and ileal CD (P=0.01). Non-inflamed ileal mucosa from CD patients carrying any of the common disease-predisposing NOD2 variants (R702W, G908R, 1007fs) had significantly reduced levels of KCNN4 mRNA expression (P=0.001). KCNN4 protein expression was detected in Paneth cells, and in T cells in inflamed lamina propria., Conclusions: Our data implicate the role of KCNN4 in ileal CD. The dual roles of KCNN4 in Paneth cell secretion and T-cell activation and also its nature as a potassium channel make it an important and practical therapeutic target.