Thyroid hormone can affect every metabolic function in your body. Your thyroid gland regulates energy and heat production, growth, tissue repair and development, and stimulates protein synthesis. Thyroid hormone modulates carbohydrate, protein and fat metabolism, vitamin uses, digestion, production of energy in the cells, muscle and nerve action, blood flow, hormone excretion, oxygen utilization and sexual function.
Thyroid stimulating hormone (TSH) is made in your pituitary gland located in your brain. TSH stimulates the thyroid gland to produce thyroid hormone. The major thyroid hormone made in the thyroid gland is thyroxine (T4). Triiodothyronine (T3) is made in other tissue from T4. T3 is five times more active than T4, however T4 can also be converted to reverse T3 (RT3) which is an inactive form. There are many factors that affect the production of thyroid hormone and the conversion of T4 to T3. Among these are deficiency of certain vitamins and minerals, imbalance of sex hormones, diet, heavy metals and environmental toxins, cortisol levels, medications, fasting, diabetes and prolonged illness.
Symptoms of Low Thyroid
Some of the symptoms of low thyroid production are depression, weight gain, constipation, headaches, brittle nails, dry skin, menstrual irregularities, fluid retention, poor circulation, hair loss, anxiety/panic attacks, decreased memory, inability to concentrate, muscle and joint pain, reduced heart rate, swollen eyelids, decreased sexual interest, cold intolerance, cold hands and feet, insomnia, fatigue, low body temperature, low blood pressure, muscle weakness, muscle cramps, carpel tunnel syndrome.
Thyroid function can be done with a blood test. This should check TSH, Free T4 (FT4), Free T3 (FT3), and thyroid antibodies.
TSH, FT4, and FT3 can also be checked by means of a blood spot test. Quite often thyroid conditions are based on just a TSH level or a TSH and T4 level. It is important to measure FT3 as this is the active hormone. Sufficient levels of FT4 can lower TSH levels to optimum but if you are not converting your FT4 to FT3 you will still suffer from clinical hypothyroidism. Reverse T3 which is an inactive form of T3 is often useful but may be difficult to obtain as many labs have discontinued providing this test.