Thyroid stimulating hormone is made by the thyroid gland and is released into the blood where it is delivered to tissues in the body. It helps the body stay warm, use energy, and keeps the brain, heart, muscles, and other organs working as they should. TSH can serve as an ‘early warning system’ in the body because it will indicate early changes in thyroid function before thyroid hormones become too high or too low. Because of this, measuring the TSH level in a blood sample is considered the best way to initially test thyroid function.
High TSH levels: The pituitary gland produces more TSH when the thyroid gland does not produce enough hormones. High levels are an indication that the thyroid gland is not making enough thyroid hormone (primary hypothyroidism).
Low TSH levels: Low TSH levels are an indication that the thyroid is producing too much thyroid hormone (hyperthyroidism or overactive thyroid). Low TSH may result from an abnormality in the pituitary gland. This abnormality prevents it from making enough TSH to stimulate the thyroid.
Symptoms of high TSH levels:
- Rapid heartbeat
- Muscle weakness
- Nervousness or irritability
- Insomnia
- Frequent bowel movements or diarrhea
- Weight loss
- Mood changes
Symptoms of low TSH Levels:
- Weight gain
- Fatigue
- Swelling of face
- Sensitivity to cold temperatures
- Slow heart rate
- Dry skin
- Depression
- Constipation
Thyroid peroxidase is an enzyme found in the thyroid gland. It plays an important role in production of thyroid hormones. A thyroid peroxidase antibody (TPOAb) test detects antibodies against TPO in the blood. If there is a presence of TPO antibodies in your blood, it could be a sign of an autoimmune disorder or may increase the risk of future thyroid disorders.
When the levels are mildly elevated, this can be caused by many thyroid conditions like thyroid cancer, type-1 diabetes, rheumatoid arthritis, as well as auto-immune collagen vascular disease.
High levels of TPO antibodies are usually caused by an autoimmune disease like Hashimoto Thyroiditis, Graves Disease, pernicious anemia, lupus and rheumatoid arthritis. It has been reported that almost 3% of people who have a positive TPO test result do not show any symptoms.
The TPO antibody test is often used to help diagnose Hashimoto’s thyroiditis. The symptoms that may be indicative of Hashimoto’s thyroiditis include:
- Fatigue
- Menstrual irregularities
- Dry skin
- Brittle nails
- Constipation
- Cold intolerance
- Muscles aches and pains
- Depression
- Brain fog
The thyroid produces a hormone called triiodothyronine, known as T3. Most of the T3 in your body binds to protein. The T3 that doesn’t bind to protein is called Free T3. It helps regulate the speed with which the cells/metabolism work. It also regulates your heart rate and how fast your intestines process food. Measuring T3 in the blood is a way to determine if there is a thyroid problem.
High levels of Free T3 levels cause an excessively high metabolic rate and increased risk of hyperthyroidism.
Low levels of Free T3 levels cause slowed metabolic rate and may be a sign of hypothyroidism.
Symptoms of high levels of Free T3 levels:
- Rapid heart rate
- Elevated blood pressure
- Anxiety
- Increased sweating
- Insomnia
- Weight loss
Symptoms of low levels of Free T3 levels:
- Fatigue
- Weight gain
- Puffy face
- Trouble tolerating cold
- Constipation
- Dry skin
- Thinning hair
- Depression
- Slowed heart rate
T4, also called thyroxine, is the main form of thyroid hormone made by the thyroid gland. T4 is mostly bound to proteins with a small amount unbound, or free. This test measures the amount of free/or unbound T4 circulating through the blood and indicates how well the thyroid gland is functioning.
High levels of Free T4 may be caused by certain thyroid problems such as thyroiditis, a goiter, high levels of protein in the blood, and hyperthyroidism.
Low levels of Free T4 may be caused by fasting, malnutrition, iodine deficiency, medication that affects protein levels, illness, pituitary problems, and hypothyroidism.
Symptoms of high Free T4:
- Anxiety
- Unplanned weight loss
- Tremors
- Diarrhea
Symptoms of low Free T4:
- Weight gain
- Fatigue
- Hair loss
- Low tolerance for cold temperatures
- Irregular period
- Constipation