Thyroid hormone levels predict the change in body weight: a prospective study

Area of Science:

• Endocrinology
• Metabolic Health
• Population Health

Background:

• Cross-sectional studies indicate a correlation between lower thyroid hormone levels and higher body mass index.
• The potential causal relationship between thyroid function and obesity risk requires further investigation.

Purpose of the Study:

• To investigate the association between thyroid function and the risk of developing obesity in a prospective cohort.
• To explore the relationship between thyroid hormones, anthropometric parameters, and obesity development over time.

Main Methods:

• A population-based prospective study involving 937 participants from the Pizarra Study, with follow-up measurements on 784 individuals after 6 years.
• Measurements included anthropometric parameters, thyroid hormone function (FT3, FT4), urinary iodine, leptin, and adiponectin.

Main Results:

• Individuals in the highest quartile of free triiodothyronine (FT3) or free thyroxine (FT4) had a significantly higher odds ratio of becoming obese.
• Higher FT3 levels at follow-up were associated with greater weight gain.
• Leptin correlated with thyrotropin and FT4, while adiponectin correlated with FT3. Urinary iodine showed a negative correlation with BMI and weight increase.

Conclusions:

• Thyroid hormone level changes may be a consequence, not a cause, of weight gain and obesity.
• Shared pathophysiological mechanisms might influence both obesity development and thyroid hormone patterns.