Thyroid function test algorithm

Thyroid is a small butterfly shaped gland in front of your neck, below the Adam’s apple. Thyroid gland is activated by TSH- thyroid stimulating hormone for thyroid hormones T3 and T4 production. TSH is an another thyroid hormone and produced by pituitary gland in your brain.

thyroid function test

T3- triiodothyronine and T4 are thyroid hormones and have so many important functions in your your body.

Thyroid hormone functions in body

Thyroid hormones regulates

  • Body temperature
  • Energy production
  • Energy usage
  • Carbohydrate metabolism
  • Metabolic rate
  • Baby growth- brain development
  • Blood pressure
  • Heart rate
  • Bone development
  • Fertility


Thyroid gland disorder and symptoms

Thyroid gland may be underactive- hypothyroidism and overactive- hyperthyroidism. Irregular thyroid function may cause several problems and symptoms in your body like;

  • Weight gain
  • Weight loss
  • Rapid heart beat
  • Decreased heart rate
  • Hand tremors
  • Sweating
  • Frequent bowel movements
  • Constipation
  • Irregular menstruation
  • Numbness in hands
  • Muscle aches
  • Joint aches
  • Memory problems
  • Infertility
  • Dry skin
  • Depression
  • Heat intolerance
  • Enlargement of thyroid gland
  • Increased appetite
  • Increased cold sensitivity
  • Hoarseness
  • Hair loss

Thyroid function tests algorithm

Thyroid function tests should be done in an order to prevent unneeded test request. TSH test should be done in first step then other tests are done according to TSH test result. Here you can see thyroid function tests algorithm and thyroid blood tests order;

If TSH is low than 0.1 mIU/L; T4 test is done to search  hyperthyroidism. If T4 level is normal then T3 blood test is done.

If TSH is low than 0.3 mIU/L; T4 test is requested because of this borderline TSH result

If TSH is between 0.3-4.2 mUI/L; other thyroid tests are not requested if you don’t have any clinical symptom

If TSH is higher than 4.2 mUI/L; higher values than 4.2 mUI/L may be related with hypothyroidism so T4 and anti-M ( anti-thyroperoxidase) tests are done

Thyroid gland disorders are diagnosed according to this thyroid function algorithm so your doctor can plan your treatment. Please consult your doctor about your test results and medication.


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