The Role of Thyroid Hormones
Thyroid hormones play critical roles throughout the body, including:
- Increasing or decreasing the heart rate
- Raising or lowering body temperature
- Regulating the caloric burn rate to influence weight gain or loss
- Regulating muscle contraction
- Controlling how quickly dying cells are replaced
- Increasing or decreasing the body temperature
This means that maintaining levels in the normal range is critical for a healthy metabolism. Unfortunately, an underactive thyroid gland frequently results in low hormone levels (known medically as hypothyroidism), particularly in women in their 30s and 40s.
What are Normal Hormone Levels?
Three hormones are usually included in thyroid function tests: Thyroid, triiodothyronine (T3), its prohormone thyroxine (T4), and thyroid stimulating hormone (TSH, which regulates the production of T3 and T4 from the thyroid gland). T4 is main circulating hormone; it gets converted into T3 in target tissues by enzymes named deiodinases. Tests measure the levels of both free and total proteins because free hormones are considered to be bioavailable . Regular thyroid function tests are particularly important in individuals receiving testosterone-based hormone-replacement therapy Since some long term users have reduced thyroid function and hypothyroidism .
The normal and reference ranges used by Quest Diagnostics for T3, T4, and TSH are shown below.
|Test||Normal Serum Concentrations|
|Total T4||5.6 to 13.7 ng/dL|
|>Free T4||0.8 to 2.7 ng/dL|
|TSH||0.4 to 4.2 mU/L|
|Total T3||76 to 181 ng/dL|
|Free T3||2.3 to 4.2 pg/mL|
Symptoms of Low Thyroid Hormones
The common symptoms of hypothyroidism, many of which are the result of a slow metabolism, are as follows:
- Cold feet and hands
- Hair loss or thinning
- Weight gain and difficulty losing weight
- Chronic fatigue
- Muscle cramps
- Persistent lower back pain
- Joint stiffness
- Easy bruising
- Mood swings
- Goiter (swelling of the throat region)
- Heavy menstrual periods
It Thyroid is important to note that not all patients who experience these symptoms and have an underactive thyroids have circulating levels outside the normal range. Unfortunately, many physicians do not treat these patients as they would a patient with overt hypothyroidism. This does not mean that you have to suffer through your symptoms. Anti-aging clinics such as AAI Clinics work with you to ensure that you reach a hormone balance that works best for you to alleviate these symptoms.
 K.A. Iwen, E. Schröder, G. Brabant, Thyroids Hormones, and the Metabolic Syndrome, European Thyroids Journal, 2 (2013) 83-92.
 M. Alen, P. Rahkila, M. Reinila, R. Vihko, Androgenic-anabolic steroid effects on serum thyroids, pituitary and steroid hormones in athletes, The American journal of sports medicine, 15 (1987) 357-361.