Obesity and Thyroid Axis.
Level 5 - mechanism / opinion, no new human data
Narrative review of physiological mechanisms without systematic search methodology or original data
PubMed 34574358 · doi:10.3390/ijerph18189434
What was done
This paper reviewed the physiological and bidirectional relationships between the hypothalamic-pituitary-thyroid axis and adiposity, focusing on the roles of thyroid hormones and thyroid-stimulating hormone in energy balance and the reciprocal impacts of obesity on thyroid function.
What was found
The abstract reports no numerical data or effect sizes. It describes mechanistic relationships: thyroid hormones influence cellular respiration, thermogenesis, resting metabolic rate, and hypothalamic appetite regulation; triiodothyronine alters adipocyte lipid turnover; and thyroid-stimulating hormone modulates lipolysis, lipogenesis, and thermogenesis. In turn, subclinical hypothyroidism can reduce basal metabolic rate and increase BMI, while obesity directly impairs thyroid function via lipotoxicity, altered adipokine profiles, and inflammatory cytokine release.
Why it matters
It highlights that thyroid dysfunction and obesity interact bidirectionally rather than through a simple one-way causal pathway, which is relevant for interpreting borderline thyroid abnormalities in individuals with obesity.
Limits
The abstract provides only qualitative narrative descriptions of biological mechanisms. It lacks systematic review methodology, quality grading of underlying studies, sample size specifications, and quantitative clinical outcome data.
Cited by
- supports Hypothyroidism can reduce basal metabolic rate by up to 25%.