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Small doses of triiodothyronine can change some risk factors associated with abdominal obesity
M Krotkiewski1, G Holm, N Shono
1Department of Rehabilitation and Medicine, Sahlgren's Hospital, University of Gothenburg, Sweden.
Objective:
To elucidate whether the administration of small doses of triidothyronine (T3) can increase concentrations of sex hormone binding globulin (SHBG) in obese women with different types of obesity and to evaluate the potential metabolic benefits of such treatment.
Design:
Daily administration of 20 micrograms of T3 during six weeks while maintaining habitual food intake and physical activity.
Subjects:
Seventy premenopausal obese women (age: 41.2 +/- 1.5 y mean +/- s.e.m., body mass index (BMI): 34.4 +/- 0.7).
Measurements:
Plasma concentrations of SHBG, lipids, insulin, thyroid hormones, sex hormones, blood glucose and insulin sensitivity (by euglycemic insulin clamp in 12 patients) at base line after six weeks of treatment.
Results:
Six weeks treatment with small doses of T3 resulted in a significant increase in plasma SHBG. The increase of SHBG was higher in abdominal obesity and not associated with a significant change in body weight, plasma insulin concentration, insulin/glucose ratio of plasma insulin sensitivity (glucose disposal during insulin clamp). In patients with initially high SHBG the significant increase of insulin removal (as judged from the increase of c-peptide/insulin ratio) was observed. Treatment resulted in a reciprocal increase of T3, decrease of thyroxine (T4), and a more than double increase of T3/T4 ratio.
Conclusions:
Administration of small doses of T3 can increase the concentration of SHBG without changing insulin concentrations or sensitivity. As there was a significant decrease (by 36%) of T4 and parallel increase of T3 with a clear increase of T3/T4 ratio it seems possible that rather than lack of thyroid hormones a lower peripheral deiodination of T4 might be a factor contributing to the low SHBG concentration in abdominal obesity. Treatment with small doses of T3 may be considered to ameliorate some of the risk factors associated with abdominal obesity, particularly in some subgroups of obese women with a relative resistance to thyroid hormones possibly dependent on decreased peripheral deiodination of thyroxine.
Insights
Small doses of triiodothyronine (T3) significantly increased sex hormone-binding globulin (SHBG) in obese women. This T3 treatment may improve metabolic risk factors associated with obesity without altering insulin sensitivity.
Area of Science:
- Endocrinology
- Metabolic Health
- Obesity Research
Background:
- Obesity is linked to altered sex hormone-binding globulin (SHBG) levels, particularly in abdominal obesity.
- Thyroid hormone metabolism, specifically peripheral deiodination of thyroxine (T4) to triiodothyronine (T3), may influence SHBG concentrations.
- Understanding the relationship between thyroid hormones and SHBG in obese individuals is crucial for metabolic health management.
Purpose of the Study:
- To investigate the effect of small-dose triiodothyronine (T3) administration on sex hormone-binding globulin (SHBG) concentrations in obese women.
- To evaluate the potential metabolic benefits, including insulin sensitivity and lipid profiles, of T3 treatment in this population.
- To explore the role of thyroid hormone metabolism in modulating SHBG levels in different obesity types.
Main Methods:
- A six-week daily administration of 20 micrograms of T3 to seventy premenopausal obese women.
- Measurements included plasma SHBG, lipids, insulin, thyroid hormones (T3, T4), sex hormones, glucose, and insulin sensitivity via euglycemic insulin clamp.
- Participants maintained their habitual food intake and physical activity levels throughout the study.
Main Results:
- Six weeks of T3 treatment led to a significant increase in plasma SHBG, with a more pronounced effect in abdominal obesity.
- No significant changes were observed in body weight, plasma insulin concentration, or insulin sensitivity.
- Thyroid hormone levels showed a reciprocal increase in T3, a decrease in T4, and a more than double increase in the T3/T4 ratio.
Conclusions:
- Low-dose T3 administration effectively increases SHBG concentrations in obese women without negatively impacting insulin levels or sensitivity.
- The findings suggest that decreased peripheral deiodination of T4, rather than a general thyroid hormone deficiency, may contribute to low SHBG in abdominal obesity.
- T3 treatment holds potential for ameliorating metabolic risk factors associated with obesity, particularly in subgroups with relative thyroid hormone resistance due to impaired peripheral deiodination.