Symptoms of thyroid dysfunction include weight gain or loss, heat or cold intolerance, palpitations, hair loss, fragile nails, easy fatigue, menstrual, bowel irregularities and mood disturbances. These symptoms are not specific to the thyroid and may be due to other causes. Blood tests for thyroid function may be useful for diagnosing thyroid disorders. These include Thyroid Stimulating Hormone (TSH), T4 and T3. TSH is produced by the pituitary gland and helps the thyroid gland develop during infancy and to produce thyroid hormones T4 and T3.
Hyperthyroidism (overactive thyroid) is likely, when T4 and/or T3 levels are high and TSH is low. Causes include Grave's disease, toxic thyroid nodule, viral thyroiditis or medication-induced. A nuclear medicine scan may help to differentiate between Grave's disease and thyroiditis. Thyroid ultrasound may show thyroid nodules or increased blood flow, suggesting thyroid inflammation.
In hypothyroidism (under-active thyroid), the TSH may be elevated, associated with low T4 or T3 levels. Causes include Hashimoto's disease, post-pregnancy, viral thyroiditis, medication-induced and rarely, cancer. Thyroid ultrasound may show a disordered glandular appearance with thyroid nodules. These nodules may need to be biopsied, depending on size, to exclude cancer.