Subclinical Hypothyroidism Linked to Metabolic Syndrome

A new study has found that the link between subclinical hypothyroidism and metabolic syndrome is only present in type 2 diabetes.

Reference: Bermúdez V, Salazar J,  Añez R, et al. Metabolic syndrome and subclinical hypothyroidism: A type 2 diabetes-dependent association. J Thyroid Res. 2018;2018:8251076. 

Valmore Bermúdez, MD, MgS, MPH, PhD, and fellow researchers in North, Central, and South America have discovered that the link between subclinical hypothyroidism (ScH) and the metabolic syndrome (MetS) is only present in conjunction with hyperglycemia in type 2 diabetes (T2DM). Click through the slides for details on their study and take home points for physicians.

Metabolic Syndrome and Hypothyroidism. MetS represents risk factors that combine to increase the risk of CV disease and T2DM, with a high prevalence in Latin America that is a major concern. ScH is defined as high TSH levels with normal free T4. Authors of the study sought to analyze the association between ScH and MetS. 

The Study. This descriptive, cross-sectional study in Venezuela selected 425 patients from a larger study based on ScH presence with 391 participants ultimately evaluated. A complete clinical history was performed by trained personnel. BMI was determined and laboratory analysis included fasting serum glucose levels, total cholesterol, HDL-C, TG, serum free T3 and T4, and TSH. 

The Results:

  • 10.5% of the evaluated population had ScH
  • 56.1% of subjects with ScH had MetS vs 38.3% of subjects with euthyroidism
  • Hyperglycemia was most frequent metabolic alteration in ScH subjects
  • Only free T3 showed lower levels in subjects with hyperglycemia, high TG, and elevated WC
  • Following multivariate analysis, hyperglycemia was the only metabolic disorder related to ScH

Take Home Points:

  • Prior reports that MetS leads to increase incidence of ScH appears unfounded
  • Hyperglycemia (MetS component) and T2DM appear to be responsible for the observed ScH increase in the study population
  • Insulin resistance and hyperglycemia should be suspected and investigated in patients with MetS components and ScH
  • Relationship between ScH and T2DM underscores need for physicians to monitor and treat hyperglycemia and diabetes
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