ECE2018 Oral Communications Benign thyroid diseases (5 abstracts)
1Leiden University Medical Center, Leiden, Netherlands; 2Bern University Hospital, Bern, Switzerland; 3Institute of Primary Health Care, Bern, Switzerland; 4Robertson Centre for Biostatistics, Institute of Health and Wellbeing, Glasgow, UK; 5School of Public Health, Cork, Ireland; 6Institute of Cardiovascular Medicine, Glasgow, UK; 7Department of Public Health and Center for Healthy Aging, University of Copenhagen, Copenhagen, Denmark.
Introduction: Although widely prescribed, the benefit of thyroid hormone replacement in subclinical hypothyroidism (SHypo) is unclear. We performed a systematic review and meta-analysis of randomized controlled trails (RCTs) to assess the impact of thyroid hormone therapy on clinical outcomes.
Methods: We followed the PRISMA guidelines and registered the study protocol on PROSPERO (CRD42017055536). We searched PubMed, Embase, Web of Science, COCHRANE Library, CENTRAL, Emcare and Academic Search Premier in April 2017. We included RCTs that assessed the impact of thyroid hormone replacement compared to placebo/no intervention in non-pregnant adults with SHypo. Data and bias-risk of included studies were extracted by two independent reviewers. Outcomes were quality of life, symptoms of depression, cognitive function, blood pressure, and the body mass index. We transformed differences in clinical scores (e.g. cognitive function) into standardized mean differences (SMD, positive values indicate levothyroxine benefit) and applied random-effects models.
Results: Overall, 19 of 2,793 initially identified studies met the inclusion criteria, with a total of 2,061 adults randomized. Levothyroxine lowered TSH into reference range in all studies, but showed no benefit regarding quality of life (five studies, SMD −0.03, 95%CI −0.10 to 0.04, I2 21%), symptoms of depression (three studies, SMD −0.14, 95%CI −0.41 to 0.12, I2 0%), and cognitive function (four studies, SMD 0.11, 95%CI −0.09 to 0.32, I2 53%). Seven studies analysed blood pressure and found no clear benefit of levothyroxine therapy compared to placebo (−0.66 mmHg, 95%CI −2.46 to 1.14 mmHg, I2 0%), and 13 evaluated the body mass index, again showing no benefit (−0.02 kg/m2, 95%CI −0.40 to 0.36 kg/m2, I2 56%). Limitations were that participants from only two smaller studies (in total 99 persons) had a mean initial TSH of >10 mU/l and that 16 out of 19 studies had an unclear or high risk of bias in at least three of the six domains of the Cochrane bias assessment.
Conclusion: This systematic review and meta-analysis does not support the use of thyroid hormone replacement therapy in adults with subclinical hypothyroidism, at least in adults with TSH <10 mU/l.