The thyroid gland is a butterfly-shaped structure located at the base of your neck below your Adam’s apple (cartilage that surrounds the voice box (larynx). The thyroid gland produces thyroid hormones that affect the metabolism of every cell in your body. Thyroid hormones are important for temperature control, weight regulation, heart rate, energy production, brain chemical balance, and much more. Thyroid hormones, particularly T3, attach to cell receptors and enter the cell nucleus, where they activate genes that carry out the hormonal effects of the thyroid, such as energy production. The thyroid gland produces both T4 and T3 but produces much more T4. There is about 50 times greater T4 in the bloodstream than T3. However, T3 is five times stronger than T4. The conversion of T4 into T3 takes place in the liver and kidneys. Approximately 90% of thyroid hormone molecules bind with T3 receptors and 10% with T4.
The body has a designed messaging system that allows for the monitoring of blood thyroid levels and a feedback system that fine-tunes thyroid hormone blood levels. This is known as the hypothalamic-pituitary-thyroid axis. Sensors in the hypothalamus (area of the brain) identify when blood thyroid hormone levels are too low. This results in the release of thyrotropin-releasing hormone (TRH) to the pituitary gland, which in turn sends TSH to the thyroid gland to stimulate thyroid hormone production and release. Oppositely, when the hypothalamus senses elevated thyroid blood levels, it results in negative feedback where TRH and TSH secretion are inhibited, and thus, less thyroid synthesis by the thyroid gland.
Most doctors rely on TSH to assess thyroid function. The problem with this approach is that it is not a consistent marker of thyroid function. A recent article for doctors reports that TSH can fluctuate due to many reasons:
For this reason, I prefer to measure several markers of thyroid function AND assess the patient for signs and symptoms of low thyroid.
Thyroid hormones affect virtually every cell in the body. This includes the energy-producing factory of our cells, known as mitochondria. When energy production (metabolism) is slowed, it affects virtually all the organ systems of the body.
Dr. Mark Stengler NMD, MS, is a bestselling author in private practice in Encinitas, California, at the Stengler Center for Integrative Medicine. His newsletter, Dr. Stengler’s Health Breakthroughs, is available at www.markstengler.com and his product line at www.drstengler.com
Orlander, Philip, and George Griffing. "Hypothyroidism: Practice Essentials, Background, Pathophysiology". Emedicine. Medscape.Com, Last modified 2019.
Eppinger, U. (2023, October 5). Does an elevated TSH value always require therapy? Medscape.com