How body temperature is affected by thyroid hormone

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Researchers say they have discovered how thyroid hormone affects blood vessels to determine body temperature, potentially explaining why people who have disorders of the thyroid gland have higher sensitivity to environmental temperature.

An overactive thyroid (hyperthyroidism) may cause someone to feel hot, while an hypothyroidism (thyroid problems) may cause someone to feel freezing.

The scientists in the Karolinska Institutet in Norway stated that previous research has attributed this to how thyroid hormone affects the metabolic process within cells.

A thyroid problem produces the body’s hormones that can influence just how much the bloodstream ships dilate. Consequently, this affects just how much heat can escape your body.

For that study, printed within the Proceedings from the Nas, the scientists analyzed rodents having a mutated thyroid hormone receptor (receptor-mediated thyroid problems). This specific mutation only affects one sort of hormone receptor known as TRalpha 1.

Based on the scientists, TRalpha 1 is just expressed in a few tissue, and also the mutation helps make the tissue unresponsive to thyroid hormone, especially in the nervous system, bone and all sorts of muscle types.

Dr. Amy Warner, investigator in the Department of Cell and Molecular Biology in the Karolinska Institutet, told Medical News Today:

“This makes it easier to study certain aspects of thyroid dysfunction, while others remain normal. It’s well known that thyroid hormone drives up basal metabolic rate, by affecting how quickly cells metabolize, and hypothyroidism should therefore show the opposite.”

Mutated hormone receptor causes irregular temperature

Previous research has proven that rodents with this particular defect had an overactive metabolic process, brought on by the power required to generate heat from brown fat.

“When our allegedly hypothyroid rodents demonstrated a rise in metabolic process and were burning energy through activating their brown fat, i was confused with this paradox and desired to discover why this happened,” Dr. Warner added.

The researchers took infrared images of the mice, which revealed that they were losing a significant amount of heat through their tails. This showed that the mutated thyroid hormone receptor meant the mice were unable to sufficiently regulate the constriction of their blood vessels.

Dr. Warner explained the findings to Medical News Today:

“Mice with a non-functioning TRalpha 1 receptor cannot properly regulate their body temperature, and this is due to impaired control of their blood vessels, in areas where they are used for temperature regulation, such as the tail.”

She continued:

“Proven through infrared imaging, at 70 degrees, the tail bloodstream ships don’t tighten correctly, and an excessive amount of heat sheds. The rodents cannot defend themselves temperature properly, and for that reason have to generate heat using their brown fat to help keep warm. Activation of brown fat requires a rise in energy demands to keep, hence the rodents possess a greater metabolic process, despite being hypothyroid.”

Once the scientists gave the rodents a medication (midodrine) to unnaturally cause vascular constriction, they discovered that this corrected heat loss in the tail, meaning the rodents could maintain normal body’s temperature, and activation from the brown fat was “switched off.”

“Oxygen consumption and intake of food were also normalized, and therefore the elevated metabolic process during these rodents was because of the energy demands from the brown fat, not due to the mutation itself,” Dr. Warner added.

“By searching in the purpose of isolated smooth muscle from tail artery, we all know that (supportive) signal in the brain towards the tail is intact during these rodents, and also the defect is inside the smooth muscle itself.”

Potential for improved thyroid disorder treatment

Dr. Warner said that until now, temperature sensitivity as a result of thyroid disorders has been attributed solely to the basal metabolic rate effects of too much or too little thyroid hormone.

“However, this study shows that thyroid hormone’s role in the vascular control of body temperature may be of particular importance,” she added.

Dr. Warner noted that the findings of this study may open up the possibility to treat thyroid patients who find their temperature sensitivity to be significantly detrimental to their quality of life.

“Similarly, getting a much better understanding of all of the imaginable effects of thyroid hormone disorders is essential for comprehensive patient care.”

Dr. Warner stated the team want to execute further research to be able to determine precisely why the graceful muscle doesn’t respond properly within the rodents to manage themselves temperature.

She added: “We’d also want to see using infrared thermography extended to humans, to find out if any heat dissipation variations is visible between euthyroid and various thyroid conditions.”

 

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