Symptoms of Low Thyroid Hormone

Thyroid Hormone

The thyroid gland produces two hormones (T4 and T3) that control body development, growth, and metabolism. More than 90% of the hormones secreted by the thyroid is T4 (thyroxine); however, T4 is mostly inactive. To become active, T4 must be converted by the body into its active form, T3 (triiodothyronine). Regulation of thyroid hormone is controlled by the brain (via the hypothalamus and pituitary), the thyroid gland itself, and peripheral conversion of inactive T4 into active T3. Therefore, low thyroid (hypothyroid) symptoms can result from multiple causes:

• a problem in the brain
• a problem in the thyroid gland
• poor conversion of thyroid hormone from T4 into T3

Thyroid hormone is essential for contraction of your heart; low thyroid hormone (“hypothyroidism”) can cause heart enlargement, congestive heart failure, and low pulse rate. Hypothyroidism can also cause high LDL (“bad”) cholesterol, the type of cholesterol that can become oxidized, leading to plaques in the arteries or "atherosclerosis."Thyroid hormone is needed by every cell of your body. Without it, cells cannot function normally—this is why thyroid hormone deficiency can cause problems in nearly every body system. Thyroid hormone is the main hormone responsible for your metabolism and energy level. It’s also critical for normal immune function, as well as healthy skin, hair, and nails. 

Muscles require thyroid hormone for strength and function—in fact, insufficient production of thyroid hormone is commonly associated with muscle aching or weakness.

Lastly, thyroid hormone is vital for the health of your brain—it maintains a positive, stable mood and improves the speed of thinking. Without enough thyroid hormone, you can become depressed or anxious. This is in part due to T3 (active thyroid hormone) working between neurons to regulate the amount and activity of neurotransmitters (brain chemicals) such as serotonin and GABA.[i]^,[ii]

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[i] Kirkegaard C, Faber J. The role of thyroid hormones in depression. Eur J Endocrinol. 1998;138(1):1–9.

[ii] Dratman M, Gordon J. Thyroid hormones as neurotransmitters.  Thyroid.  1996;6(6):639–47. 

Watch Dr. Retzler discuss symptoms of Low Thyroid Hormone at a recent HormoneSynergy Seminar in Portland Oregon