Hormonal
In euthyroid middle-aged adults, higher free T3 levels and a higher FT3-to-FT4 ratio are positively associated with unfavorable metabolic profiles (higher BMI, waist circumference, triglycerides, blood pressure, fasting glucose, and lower HDL) and increased cardiovascular risk markers (IL-6, hs-CRP, pulse wave velocity).
If you are in the middle-aged range and have metabolic issues (high blood pressure, high triglycerides, central obesity) despite having 'normal' thyroid labs, the ratio of your Free T3 to Free T4 might be a contributing factor. A higher ratio (driven by higher T3 or lower T4) is linked to worse metabolic markers. This suggests that 'normal' TSH doesn't guarantee optimal metabolic health, and the internal conversion of T4 to T3 matters.
(F) T3 and the FT3-to-FT4 ratio were positively related to BMI, waist circumference and components of the metabolic syndrome, i.e. triglycerides, systolic and diastolic blood pressure and fasting plasma glucose, and negatively with HDL-cholesterol levels, whereas FT4 was negatively associated with BMI, waist circumference and triglycerides (all p-values <0.001).
Why this rating
Large cross-sectional study (n=2315) with robust adjustments, but causality cannot be established.
Source
Triiodothyronine and Free Thyroxine Levels are Differentially Associated with Metabolic Profile and Adiposity-Related Cardiovascular Risk Markers in Euthyroid Middle-Aged Subjects
Greet Roef et al. · Thyroid · 2013
DOI 10.1089/thy.2013.0314
More from this paper
- Lower Free T4 (FT4) levels within the euthyroid range are negatively associated with BMI, waist circumference, and triglycerides, and positively associated with HDL-cholesterol.Good
- Higher TSH levels within the normal reference range are positively associated with total cholesterol, triglycerides, and blood pressure.Good
Related findings · Hormonal
- Initial treatment for type 2 diabetes should be a combination of metformin and either an SGLT-2 inhibitor or a GLP-1 receptor agonist to achieve cardiorenal protection, rather than monotherapy or older agents like sulfonylureas.Strong
- For patients with specific monogenic obesity syndromes (leptin deficiency, POMC/PCSK1/LEPR mutations), targeted pharmacotherapy (recombinant leptin or setmelanotide) is highly effective and should be prioritized, unlike in polygenic obesity.Strong
- Continued weekly administration of 2.4 mg subcutaneous semaglutide prevents weight regain and promotes further weight loss in adults with overweight or obesity, whereas switching to placebo results in significant weight regain.Strong
This is one finding among thousands. Every one is graded and traced to its source, so you can see what the evidence actually supports. Browse the research →