A standard thyroid panel include TSH (thyroid stimulating hormone) and T3 only.
When symptoms of hypothyroidism persist in spite of normal lab tests functional medicine consi…ders the following hypothyroid patterns:
1. Hashimoto’s or autoimmune thyroiditis – the cause is the abnormal reaction of the immune system.
2. pituitary gland dysfunction can be caused by chronic stress, hypoglycemia, insulin resistance, infection and pregnancy – TSH is below the functional range (1.8-3.0) but within standard range (0.5-5.0), T4 will be low in both.
3. under-conversion of T4 to T3 – the inactive T4 must be converted to the active T3 in the liver and the gastrointestinal system. Inflammation and elevated cortisol levels release inflammatory substances that damage cell membranes and supress the body’s ability of converting T4 to T3.
4. Thyroid resistance – thyroid gland function and lab test markers are normal but resistance is caused by high cortisol levels, chronic stress, high homocysteine levels and genetic predisposition.
5. Elevated TBG (thyroid hormone binding globulin) binds and transports thyroid hormone and levels of free thyroid hormone will be low. TSH and T4 levels will be normal, but T3 will be low. Elevated TBG is caused by high estrogen levels associated with hormone replacement therapy and birth control pills.
6. Decreased TBG – free T3 levels are high in this case, but it will cause cells to develop resistance to it. Decreased TBG levels are caused by high testosterone levels, type II diabetes, insulin resistance and in women with POCS (polycystic ovary syndrome)
Thyroid physiology is very complex and needs a comprehensive diagnosis to see why some people struggle with symptoms they have.