Hormonal
Intracellular regulation of thyroid hormone by deiodinases (D1, D2, D3) dictates tissue-specific metabolic outcomes, where local T3 activation promotes energy expenditure and lipid mobilization, while inactivation preserves energy stores.
Your body's metabolic rate isn't just determined by your thyroid gland's output, but by how your specific tissues process that hormone. Enzymes called deiodinases activate or deactivate thyroid hormone locally in organs like muscle and fat. This means two people with identical blood thyroid levels can have vastly different metabolic rates and fat storage tendencies depending on their tissue-specific enzyme activity.
Thyroid hormones (THs) are key determinants of cellular metabolism and regulate a variety of pathways that are involved in the metabolism of carbohydrates, lipids and proteins in several target tissues. Notably, hyperthyroidism induces a hyper-metabolic state characterized by increased resting energy expenditure, reduced cholesterol levels, increased lipolysis and gluconeogenesis followed by weight loss, whereas hypothyroidism induces a hypo-metabolic state characterized by reduced energy expenditure, reduced lipolysis and gluconeogenesis followed by weight gain.
Why this rating
Based on a review of multiple mouse models and human genetic associations, though it is a mini-review rather than primary clinical trial data.
Source
Metabolic Effects of the Intracellular Regulation of Thyroid Hormone: Old Players, New Concepts
Annunziata Gaetana Cicatiello et al. · Frontiers in Endocrinology · 2018
DOI 10.3389/fendo.2018.00474
More from this paper
- Brown Adipose Tissue (BAT) activity and adaptive thermogenesis are critically dependent on local Type 2 Deiodinase (D2) activity converting T4 to T3, particularly in response to cold exposure.Good
- Type 3 Deiodinase (D3) inactivation of thyroid hormone is essential for pancreatic beta-cell maturation and insulin secretion; D3 deficiency leads to glucose intolerance and impaired insulin secretion.Good
- Local thyroid hormone activation in skeletal muscle via D2 drives a shift from slow-twitch (Type I) to fast-twitch (Type II) fibers, increasing energy expenditure and influencing insulin sensitivity.Good
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