Hypothyroidism (low thyroid function) affects over 200 million people worldwide and is responsible for a variety of seemingly unrelated health conditions ranging from fatigue to difficulty losing weight. The main role of your thyroid gland is to regulate your metabolic rate, or the speed at which your body operates. Nutritional deficiencies in iodine, selenium, zinc and tyrosine can directly contribute to hypothyroidism, making everything run slowly in your body.
What does your thyroid do?Your thyroid is a small butterfly shaped gland made up of small sacs (thyroid follicles) located at the front of your neck, just under your voice box, and is responsible for producing two important hormones; T3 (triiodothyronine) and T4 (tetraiodothyronine or thyroxine). The thyroid is controlled by two areas in your brain; anterior pituitary gland responsible for producing thyroid stimulating hormone (TSH) and the hypothalamus which produces thyroid releasing hormone (TRH). These hormones act as ‘chemical messengers’, sending messages to a wide variety of cells throughout your body. When low levels of thyroid hormone are detected in your blood, your hypothalamus and pituitary glands go into action; TRH is released stimulating TSH, signalling the thyroid to release T3 and T4. When your blood levels of thyroid hormone return to normal, production of TRH and TSH cease. This feedback system is called the hypothalamus–pituitary–thyroid axis (HPT axis) and is responsible for monitoring and controlling thyroid hormones.
Thyroid Hormones T3 and T4T3 and T4 are so named because T3 contains 3 iodine molecules and T4 contains 4 iodine molecules. 20% of T3 and 80% of T4 are made from a protein called thyroglobulin, which is stored in the thyroid follicles. T4 is converted into the more active T3 in the liver, kidneys and many other cells in your body. T3 is between 5-7 times stronger than T4 with 85% of T3 made from T4 and the remaining 15% made by the thyroid gland. The thyroid itself produces very little T3.
How hypothyroidism affects your bodyMany of the cells in your body have thyroid hormone receptors such as the liver, adrenals, immune and reproductive systems giving hypothyroidism a wide range of activity in slowing everything down in your body including:
- fatigue & tiredness
- difficulty losing weight
- poor memory & concentration
- poor digestive function & constipation
- low libido
- increased sensitivity to cold
- dry, rough skin & brittle nails
- coarse, brittle hair or hair loss
- menstrual abnormalities & infertility
- high cholesterol & triglycerides
- fluid retention & puffiness
Hypothyroidism and nutritional deficienciesNutritional deficiencies play a key role in hypothyroidism:
- Iodine is crucial for thyroid hormone production and is the key component of T3 and T4. Iodine deficiency contributes to around 95% of cases of hypothyroidism.
- Selenium is essential for the conversion T4 into the active form, T3. Without selenium this conversion cannot take place.
- Zinc deficiency adversely affects thyroid hormone levels and the conversion of T4 into T3.
- Tyrosine is important for the production of thyroglobulin, the protein required for the production of T3 and T4. Your thyroid gland adds iodine to the tyrosine molecule to produce thyroid hormones.