How the Brain Controls Thyroid Hormones?

How the Brain Controls Thyroid Hormones?

Anil Kumar, PhD
Created On
Nov 26 2021
Last Updated
May 26 2022

Introduction

Thyroid is a butterfly shaped gland located in the throat, next to Adams apple. Despite its small size, thyroid is one of the most important glands.

It plays several important roles. It is critical for a baby's development during pregnancy, in maintaining body temperature, for an optimal metabolism, in helping maintain weight, for good mental health, and to resist various food and outdoor allergies.

Several glands and multiple hormones work together to efficiently run a closed loop system for proper thyroid function.

Thyroid dysfunction has wide range of symptoms and a thyroid test can help in conforming potential issues.

Thyroid and the Brain

Hypothalamus, located in the back of our brain, is the control center for many hormones. Based on daily activities, diets, mood, and health status, hypothalamus acts as a big switch that controls several critical functions in the body. For example, it releases a key hormone called TRH (thyrotropin-regulating hormone) to regulate thyroid function.

TRH directs the pituitary, another important gland near hypothalamus, to release TSH (thyroid stimulating hormone). Once thyroid recognizes the release of TSH, it adjusts the flow to two important hormones: T4 and T3.

T4, or thyroxine, has four iodine atoms. Upon the loss of one iodine atom, it converts to T3, or tri-iodo-thyronine. T3 is the more active in the tissues. However, T4 levels are used to assess the health of thyroid gland.

Once optimal levels of T4 and T3 are maintained in the blood, the hypothalamus tracks them for a controlled release of TRH and TSH. Therefore, an efficient closed-loop is formed that maintains optimal levels of thyroid hormones in the body.

Thyroid Dysfunction

The hypothalamus-pituitary-thyroid closed loop (often called HPT axis) is quite resilient in efficiently maintaining optimal hormone levels.

Whenever a problem in the thyroid or pituitary appears, this closed loop compensates for any deficiency or overflow. For example, whenever T4 levels are low, say, due to problems with the thyroid gland, pituitary will release more TSH in order to compensate the low levels.

Despite such an efficient HPT axis, 1 in 25 people face some thyroid related issues in their lifetime.

These may be due to insufficient thyroid hormones, a condition called hypothyroidism. Or an excess thyroid hormone release, during hyperthyroidism.

As long as the glands can compensate for each other, healthy levels can be maintained and these subclinical conditions are not life threatening. However, when the normal TSH, T4 or T3 levels can no longer be maintained, despite compensation, this loop starts to malfunction. The result is an overt or clinical thyroid problem.

Symptoms

The symptoms of thyroid problems manifest in several ways. At first, they are mild, e.g., as anxiety, irritation, increase in weight, loss of appetite, feeling of unusually hot or cold, slow muscle responses, stiff joints, skin rashes, or hair loss.

Over period, they can result in serious and life-threatening conditions, such as, heart problems, high cholesterol, high blood pressure, allergies, anemia, sleep apnea, and an unusual enlargement of the thyroid gland—a condition called goiter.

The biggest offender in causing thyroid problems is lack of iodine. Iodine deficiency has been such a big public health concern that governments across the world often mandate a daily minimum iodine supply through fortification of salt.

Insufficient iodine can cause serious problems during pregnancy. A child’s IQ can be irreversibly impacted by mother’s thyroid problems during pregnancy. Thyroid hormones fluctuate significantly during pregnancy and require careful monitoring for each trimester.

Although thyroid problems increase with age, women are at four-times higher risk than men.

Surprisingly, thyroid disorders often appear in women during youth and might cause serious problems to their new born babies, if not monitored properly. A thyroid blood test is fairly common and can be easily performed from home with a simple finger prick sample.


thyroid-test

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