How is it Diagnosed?
Hypothyroidism is diagnosed primarily through clinical evaluation and blood tests that
assess thyroid function. Physicians begin by reviewing the patient’s symptoms, such as
fatigue, weight gain, constipation, dry skin, cold intolerance, and depression. A physical
examination may reveal signs like slow heart rate, puffiness, hair thinning, or a swollen
thyroid (goiter).
The key diagnostic test is the serum Thyroid Stimulating Hormone (TSH) test. In primary
hypothyroidism, TSH levels are elevated due to the pituitary gland's attempt to
stimulate an underactive thyroid. Alongside, Free Thyroxine (Free T4) levels are
measured. A low Free T4 confirms the diagnosis. In secondary hypothyroidism (due to
pituitary or hypothalamic dysfunction), both TSH and Free T4 may be low.
Additional tests include anti-thyroid peroxidase (anti-TPO) antibodies, which help
diagnose autoimmune thyroiditis (Hashimoto’s thyroiditis), the most common cause.
Lipid profiles and complete blood counts may be ordered to assess related
complications like hyperlipidemia or anemia.
Ultrasound of the thyroid is not routine but may be performed if nodules or structural
abnormalities are suspected. In some cases, a radioactive iodine uptake scan may be
recommended to evaluate thyroid activity, though this is more common in
hyperthyroidism.
Regular follow-up testing is essential to monitor treatment response and adjust
levothyroxine doses.