The relationship between thyroid function and body weight is bidirectional and complex.
It is known for decades, if not centuries, that cretinism (only in the end of the 19th century to be associated to hypothyroidism) may be accompanied by weight gain and that thyrotoxicosis may result in weight loss. As early as in 1835 Robert J. Graves described that ladies affected by goitre and palpitations (probably due to hyperthyroidism resulting from the disease which is now named after him) were remarkably thin . Five years later the German physician Karl von Basedow described the same condition, where a lady suffering from goitre, Exophthalmos and palpitations had severely emaciated . In 1883 the swiss surgeon Theodor Kocher described weight gain after total thyroidectomy . Ten years later, in 1893 William Ord described rapid weight loss, after myxoedematous patients were set on treatment with thyroid extreact .
Today it is known that over one third of hypothyroid infants have a birth weight greater than the ninetieth percentile [6, 7]. However, an “atypical” form of hypothyroidism may be associated to low birth weight . Of course, weight gain in hypothyroidism isn’t restricted to infants, but common in adults, too. Hypothyroidism is assumed to contribute 2.5 to 5 kg (5 to 10 pounds) to body weight .
On the other hand, changes in body weight may also result in changes of thyroid function. A number of studies, as recently extensively reviewed [10, 11], described elevated TSH levels and increased total step-up deiodinase activity in patients with weight gain. These changes were reversible after weight loss . On the other hand, low T3 syndrome is a well-known consequence of anorexia and starvation [13, 14].
Probably, these changes represent adaptive responses of pituitary-thyroid axis to type 1 or type 2 allostasis, respectively . The observed mechanisms may contribute to some kind of autoregulation of weight in conditions of changing supply with energy.
To use thyroid hormones as an adjunct treatment in obesity is strongly discouraged, since cardiovascular side effects may be significant .
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9: American Thyroid Association: Thyroid & Weight. 2016. https://www.thyroid.org/wp-content/uploads/patients/brochures/Thyroid_and_Weight.pdf
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childhood obesity and metabolic comorbidity. Clin Chim Acta. 2012 Feb
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11: Fontenelle LC, Feitosa MM, Severo JS, Freitas TE, Morais JB, Torres-Leal FL,
Henriques GS, do Nascimento Marreiro D. Thyroid Function in Human Obesity:
Underlying Mechanisms. Horm Metab Res. 2016 Dec;48(12):787-794.
PMID: 27923249. https://www.ncbi.nlm.nih.gov/pubmed/27923249
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25;316(2):165-71. doi: 10.1016/j.mce.2009.06.005.
PMID: 19540303. https://www.ncbi.nlm.nih.gov/pubmed/19540303 http://dx.doi.org/10.1016/j.mce.2009.06.005
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total starvation on the pituitary-thyroid-axis in obese individuals. Acta
Endocrinol Suppl (Copenh). 1973;173:144. PMID: 4542076. https://www.ncbi.nlm.nih.gov/pubmed/4542076
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Braverman LE. The effect of starvation on the concentration and binding of
thyroxine and triiodothyronine in serum and on the response to TRH. J Clin
Endocrinol Metab. 1974 Jul;39(1):191-4. PMID: 4835133. https://www.ncbi.nlm.nih.gov/pubmed/4835133
15: Chatzitomaris A, Hoermann R, Midgley JE, Hering S, Urban A, Dietrich B, Abood
A, Klein HH, Dietrich JW. Thyroid Allostasis-Adaptive Responses of Thyrotropic
Feedback Control to Conditions of Strain, Stress, and Developmental Programming.
Front Endocrinol (Lausanne). 2017 Jul 20;8:163. doi: 10.3389/fendo.2017.00163.
PMID: 28775711; PMCID:
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