By: Krista Borowski, RPh
Thyroid dysfunction, specifically hypothyroidism, is commonly under-diagnosed, but can account for a wide variety of symptoms. The common symptoms of hypothyroidism are (but not limited to) fatigue, weight gain, brittle hair and nails, hair loss, cold sensitivity, constipation, depression, muscle and joint pain, and menstrual irregularities. There are several situations that can contribute to less than optimal thyroid function:
- Autoimmune reactions
- Inadequate production of T4
- Poor conversion of T4 to T3
- Poor receptor function
The thyroid gland influences many functions in the body, especially metabolic rate.
The hormones thyroxine (T4) and triidothyronine (T3) are secreted from the thyroid gland, with T4 being produced in greater amounts than T3. T4 is inactive and must be converted to active T3 in order to have the desired effects on the body. Thyroid hormone output is regulated by thyroid stimulating hormone (TSH) secreted from the anterior pituitary gland, which itself is regulated by thyrotropin releasing hormone (TRH) produced by the hypothalamus. TSH stimulates the thyroid gland to release thyroid hormone when it senses low levels. When there are adequate amounts of thyroid hormone available, TSH levels drop so the thyroid gland lowers the production of hormones.
When a person presents with signs of hypothyroidism, their physician will typically order a test to check the level of TSH and possibly T4. Often times these results will come back within the normal range and the patient can’t understand why they don’t feel well. If the body is unable to convert inactive T4 into the active T3, then signs and symptoms of hypothyroidism may be present. A “poor converter” will often have normal levels of TSH and T4 because there is adequate thyroid production, but metabolic pathways are impaired. In order to get the desired metabolic effects, T4 must be converted into T3 by the enzyme 5’ deiodinase. There are also instances where T4 is bound in the serum so it is less available for the conversion to T3. There are several factors that can inhibit the conversion of T4 to T3 which include:
- Advanced age
- Stress and high cortisol
- Chronic inflammation or infection
- Vitamin and mineral deficiencies (selenium, zinc, vitamins A, B6 and B12)
- Drugs (beta-blockers, oral contraceptives, oral estrogen used for hormone replacement therapy, chemotherapy, lithium, low progesterone)
When checking thyroid function, there are other tests that should be done if TSH and T4 appear normal, but the person has symptoms of hypothyroidism. These include free T4, free T3 and TPOab. Free T4 is the non-protein bound fraction of T4 that is available for conversion to T3. Free T3 is the active thyroid hormone that regulates the metabolic activity of the cells. TPOab (thyroid peroxidase antibodies) will indicate the presence of an autoimmune reaction. ZRT Laboratory offers a Blood Spot Test Kit that includes all the mentioned tests. Once one has a more complete picture of thyroid function, their health care provider can work with them on how best to treat any thyroid dysfunction. MD Custom Rx is well versed in assisting providers and patients with information, test kits, compounded thyroid medications, and any supplements that may be needed.