Serum thyroid-stimulating hormone (TSH) testing is the best screening tool for thyroid
dysfunction. When TSH levels are in the reference range, additional tests such as free
thyroxine, free triiodothyronine or thyroid antibodies rarely add value, except in
patients with pituitary disease, when TSH is unreliable.
Overt hypothyroidism and subclinical hypothyroidism with TSH levels > 10 mU/L can
be treated without further investigation. The health impact of subclinical
hypothyroidism with mildly elevated levels of TSH (4–10 mU/L) remains uncertain,
particularly in older people; treatment or observation are reasonable options.
Thyroxine remains standard treatment for hypothyroidism, with optimal dosage
determined by clinical response and serum TSH.
Hyperthyroidism is commonly caused by Graves’ disease, thyroiditis or toxic nodular
goitre. The cause should be established before offering treatment. Radionuclide
scanning is the imaging modality of choice. Positive TSH-receptor antibodies indicate
Thyroid ultrasound is indicated for assessment of palpable goitre and thyroid nodules.
It is not part of routine assessment of hyperthyroidism or hypothyroidism. Overzealous
use of ultrasound identifies clinically unimportant thyroid nodules and can lead to
overdiagnosis of thyroid cancer.
For thyroid nodules, the key investigation is ultrasound-guided fine needle aspiration
biopsy, depending on size and sonographic appearance. Biopsy should not be
performed routinely on small nodules < 1 cm. It remains controversial whether pregnant women should be screened for thyroid disease. Reference intervals for thyroid function tests during pregnancy are not well established, and it is uncertain whether thyroxine treatment for pregnant women with serum TSH levels between 2.5 and 4.0 mU/L is beneficial. Iodine supplementation is recommended during pregnancy. Comments: The face that hypothyroidism is usually caused by Hashimoto's thyroiditis when there has been no radiation or surgery therapies means the GP should refer the patient to an endocrinologist if the TSH is above 5. Anti-thyroid-antibodies and a neck examination to feel for a firm goiter or nodules is indicated as is the case finding check up of first degree relatives for autoimmune thyroid disease.Also an ultrasound of the neck is indicated if there is a firm thyroid on neck examination.