Most physicians no longer use BMR due to the complexity in doing the test and because the BMR is subject to many influences other than the thyroid state. Differences in BMRs are associated with changes in energy balance. Energy balance reflects the difference between the number of calories one eats and the number of calories the body uses. If a high BMR is induced by the administration of drugs, such as amphetamines, animals often have a negative energy balance which leads to weight loss.
Based on such studies many people have concluded that changes in thyroid hormone levels, which lead to changes in BMR, should also cause changes in energy balance and similar changes in body weight. However, BMRs are not the whole story relating weight and thyroid.
For example, when metabolic rates are reduced in animals for example by decreasing the body temperature , they often do not show the expected weight gain. Thus, the relationship between metabolic rates, energy balance, and weight changes is very complex. There are many other hormones besides thyroid hormone , proteins, and other chemicals that are very important for controlling energy expenditure, food intake, and body weight. Because all of these substances interact with the parts of the brain and body that control energy expenditure and energy intake, we cannot predict the effect of altering only one of these factors such as thyroid hormone on body weight as a whole.
Since the BMR in patients with hyperthyroidism see Hyperthyroidism brochure is elevated, many patients with an overactive thyroid do, indeed, have some weight loss.
Furthermore, weight loss is related to the severity of the overactive thyroid. Request an Appointment at Mayo Clinic. Thyroid gland Open pop-up dialog box Close. Thyroid gland Your thyroid gland is located at the base of your neck, just below the Adam's apple. Share on: Facebook Twitter. Show references AskMayoExpert. Rochester, Minn. De Leo S, et al.
The Lancet. Merck Manual Professional Version. Accessed Oct. American Thyroid Association. Hyperthyroidism overactive thyroid. Burch HB, et al. Management of Graves disease. Graves' disease. You may also experience difficulty sleeping, sensitive, thin skin, and excessive sweating.
These are all signs that you absolutely need to go to the doctor. Unchecked weight loss, whether from hyperthyroidism, a parasite, depression, or some other cause is no laughing matter. If untreated, this can lead to serious consequences from malnutrition. You can and will lose muscle and bone mass. This is dangerous. Treatment of hyperthyroidism often involves surgery to remove the overactive thyroid.
It is usually necessary to remove the entire thyroid gland. ATPO: anti-thyroperoxidase antibodies. The etiology of hypothyroidism per case was 13 patients with primary hypothyroidism anti-thyroperoxidase antibodies present in eight cases , two with amiodarone-induced hypothyroidism, one with post-surgical hypothyroidism, and one postradioiodine therapy.
When comparing basal mean weight or BMI, no significant differences were found between hypothyroid and hyperthyroid patients: Basal weight After specific treatment and normalization of thyroid hormone levels, there were still no statistically significant differences in body weight between the two groups After treatment and normalization of thyroid function of the 17 hypothyroid patients, the mean patient weight fell from After treatment and normalization of thyroid function of the 17 patients with hyperthyroidism, the mean baseline weight increased from In our study, no statistically significant differences were observed in the weight or the BMI of hypo- and hyperthyroid patients, neither at diagnosis, nor following normalization of hormone levels after treatment.
At baseline, both hypo- and hyperthyroid patient groups demonstrated a non-significant weight difference of approximately 6 kg, and a very similar BMI, respectively, with both groups falling into the overweight range. After treatment and normalization of thyroid function, the difference in weight between the two groups was further reduced. The BMI values also remained similar for both groups. In addition, after analyzing the two different types of thyroid function disorder hyper- and hypothyroidism separately, we observed statistically significant differences between baseline and post-treatment body weight and BMI.
Hypothyroid patients experienced a mean weight loss of 2. However, it is noteworthy that patients with a greater degree of hypothyroidism TSH Some authors suggest that weight gain is greater in post-surgical hypothyroidism than in autoimmune hypothyroidism.
The relationship between hypothyroidism and obesity has historically been based on studies with a baseline population selected from obese patients whose thyroid hormone levels were assessed. In several of these studies, higher incidences of hypothyroidism were found in obese patients than in the general population.
The relationship between hypothyroidism and obesity seems to be weaker than previously thought, even more in subjects with treated hypothyroidism. In the hyperthyroidism patients group, weight gain was observed on completion of treatment when the results of the thyroid function test returned to normal.
This is a common finding in the literature 13 , 15 , 20 , 21 and there are several theories regarding it. When euthyroidism is regained, weight gain occurs at the expense of both compartments. Hence, this would indicate the presence of relative hypothyroidism within the limits of analytic normality. Our study has a number of limitations that should be taken into account. In the same line, other chemistry data for example glucose and cholesterol were not available.
Another limitation to our study derives from the small number of patients finally included for analysis. However, this aspect also minimized possible biases. The reason for the high volume of pregnant patients is that the study was conducted before having specific TSH ranges for pregnancy in our population, so we used the ATA ranges. In this context, more than a third of pregnant women were above the upper limit. Otherwise, patients with stable mild chronic diseases were not excluded for example, diabetic subjects well controlled with metformin.
Another limitation is that composition body data were not recorded, nor by physical measurements like waist perimeter neither impedance techniques. In conclusion, hypothyroid and hyperthyroid patients after treatment and normalization of thyroid function have statistically significant changes in BMI, but these do not show great relevance in clinical practice because the BMI remained in the overweight range in both groups.
National Center for Biotechnology Information , U. Int J Gen Med. Published online Aug Author information Article notes Copyright and License information Disclaimer. Received Apr 16; Accepted Jul This work is published and licensed by Dove Medical Press Limited.
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