Synthetic thyroid hormone T4 in a pill form treats low thyroid function, according to WebMD. Patients who have low thyroid function, also known as hypothyroidism, require regular blood tests to determine if thyroid hormone levels are healthy or if medication needs adjustment.
Low thyroid function requires treatment to avoid complications, such as joint pain, obesity, infertility and heart problems, explains WebMD. Doctors diagnose hypothyroidism by testing thyroid-stimulating hormones and thyroxine in the body. T4 levels that are lower than normal indicate low thyroid function. Doctors also test thyroid function through a thyroid ultrasound or scan to check for inflammation or nodules.
Symptoms of a low thyroid function vary based on a patient's health condition but commonly include swelling of the thyroid gland, unexplained weight gain, constipation, dry skin and fatigue, according to WebMD. Additional symptoms include changes in menstrual cycles, depression, hair loss or dry hair, sensitivity to cold, a slow heart rate or carpal tunnel syndrome. Many patients also have difficulty losing weight when the thyroid function is low.
Women are more prone to low thyroid function, according to WebMD. People with autoimmune disorders, such as celiac disease, rheumatoid arthritis, multiple sclerosis or Type 1 diabetes, are also at risk for low thyroid function.