Related guidance:

Thyroid disease: assessment and management NICE guideline (NG145 November 2019, updated October 2023)

Indications for tests for thyroid dysfunction

  • Consider tests for thyroid dysfunction for adults, children and young people if there is a clinical suspicion of thyroid disease, but bear in mind that 1 symptom alone may not be indicative of thyroid disease.
  • Offer tests for thyroid dysfunction to adults, children and young people with:
    • type 1 diabetes or other autoimmune diseases, or
    • new-onset atrial fibrillation.
  • Consider tests for thyroid dysfunction for adults, children and young people with depression or unexplained anxiety.
  • Consider tests for thyroid dysfunction for children and young people with abnormal growth, or unexplained change in behaviour or school performance.
  • Be aware that in menopausal women symptoms of thyroid dysfunction may be mistaken for menopause.
  • Do not test for thyroid dysfunction during an acute illness unless you suspect the acute illness is due to thyroid dysfunction, because the acute illness may affect the test results.
  • Do not offer testing for thyroid dysfunction solely because an adult, child or young person has type 2 diabetes.

Tests when thyroid dysfunction is suspected

  • Consider measuring thyroid-stimulating hormone (TSH) alone for adults when secondary thyroid dysfunction (pituitary disease) is not suspected.
    Then:
    • if the TSH is above the reference range, measure free thyroxine (FT4) in the
    same sample
    • if the TSH is below the reference range, measure FT4 and free tri-iodothyronine (FT3) in the same sample.
  • Consider measuring both TSH and FT4 for:
    • adults when secondary thyroid dysfunction (pituitary disease) is suspected
    • children and young people.
    If the TSH is below the reference range, measure FT3 in the same sample.
  • Consider repeating the tests for thyroid dysfunction above if symptoms worsen or new symptoms develop (but no sooner than 6 weeks from the most recent test).
  • Ask adults, children and young people with suspected thyroid dysfunction about their biotin intake because a high consumption of biotin from dietary supplements may lead to falsely high or low test
    results.

Managing primary hypothyroidism

  • Offer levothyroxine as first-line treatment for adults, children and young people with primary hypothyroidism.
  • Do not routinely offer liothyronine for primary hypothyroidism, either alone or in combination with levothyroxine, because there is not enough evidence that it offers benefits over levothyroxine monotherapy, and its long-term adverse effects are uncertain.
  • Do not offer natural thyroid extract for primary hypothyroidism because there is not enough evidence that it offers benefits over levothyroxine, and its long-term adverse effects are uncertain. Natural thyroid extract does not have a UK marketing authorisation so its safety is uncertain.
  • Consider starting levothyroxine at a dosage of 1.6 micrograms per kilogram of body weight per day (rounded to the nearest 25 micrograms) for adults under 65 with primary hypothyroidism and no history of cardiovascular disease.
  • Consider starting levothyroxine at a dosage of 25 to 50 micrograms per day with titration for adults aged 65 and over and adults with a history of cardiovascular disease.

Follow-up and monitoring of primary hypothyroidism

  • Aim to maintain TSH levels within the reference range when treating primary hypothyroidism with levothyroxine. If symptoms persist, consider adjusting the dose of levothyroxine further to achieve optimal wellbeing, but avoid using doses that cause TSH suppression or thyrotoxicosis.
  • Be aware that the TSH level can take up to 6 months to return to the reference range for people who had a very high TSH level before starting treatment with levothyroxine or a prolonged period of untreated hypothyroidism. Take this into account when adjusting the dose of levothyroxine.
  • For adults who are taking levothyroxine for primary hypothyroidism, consider measuring TSH every 3 months until the level has stabilised (2 similar measurements within the reference range 3 months apart), and then once a year.
  • Consider measuring FT4 as well as TSH for adults who continue to have symptoms of hypothyroidism after starting levothyroxine.
  • For children aged 2 years and over and young people taking levothyroxine for primary hypothyroidism, consider measuring FT4 and TSH:
    • every 6 to 12 weeks until the TSH level has stabilised (2 similar measurements within the reference range 3 months apart), then
    • every 4 to 6 months until after puberty, then
    • once a year.
  • For children aged between 28 days and 2 years who are taking levothyroxine for primary hypothyroidism, consider measuring FT4 and TSH:
    • every 4 to 8 weeks until the TSH level has stabilised (2 similar measurements within the reference range 2 months apart), then
    • every 2 to 3 months during the first year of life, and
    • every 3 to 4 months during the second year of life.

Managing thyrotoxicosis

Initial treatment in primary/non-specialist care

  • Be aware that transient thyrotoxicosis without hyperthyroidism usually only needs supportive treatment (for example, beta-blockers).
  • Consider antithyroid drugs along with supportive treatment for adults with hyperthyroidism who are waiting for specialist assessment and further treatment.
  • Use of carbimazole is subject to MHRA advice on contraception and risk of acute pancreatitis.

Carbimazole is associated with an increased risk of congenital malformations, especially when administered in the first trimester of pregnancy and at high doses. Women of childbearing potential should use effective contraception during treatment with carbimazole. See Carbimazole: increased risk of congenital malformations; strengthened advice on contraception. (MHRA February 2019)

If acute pancreatitis occurs during treatment with carbimazole, immediately and permanently stop treatment. Re-exposure to carbimazole may result in life-threatening acute pancreatitis with a decreased time to onset. See Carbimazole: risk of acute pancreatitis. (MHRA February 2019)

  • Before starting antithyroid drugs for adults, children and young people with hyperthyroidism, check full blood count and liver function tests.
  • When offering antithyroid drugs as first-line definitive treatment to adults with Graves’ disease, offer carbimazole for 12 to 18 months, using either a block and replace or a titration regimen, and then review the need for further treatment.
  • When offering antithyroid drugs to children and young people with Graves’ disease, offer carbimazole, using a titration regimen, and review the need for treatment every 2 years.
  • When offering life-long antithyroid drugs to adults with hyperthyroidism secondary to a single or multiple toxic nodules, consider treatment with a titration regimen of carbimazole.
  • Consider propylthiouracil for adults:
    • who experience adverse reactions to carbimazole
    • who are pregnant or trying to become pregnant within the following 6 months
    • with a history of pancreatitis.
  • Stop and do not restart any antithyroid drugs if a person develops agranulocytosis. Consider referral to a specialist for further management options.

British thyroid foundation patient information leaflets 

Therapeutic AreaFormulary ChoicesCost for 28
(unless otherwise stated)		Rationale for decision / comments
Thyroid hormonesLevothyroxine25mcg tablet: £0.90
50mcg tablet: £0.81
100mcg tablet: £0.81
100mcg/5ml oral
solution sugar free: £164.99 (100ml)
as Teva®25mcg tablet: £0.80

Lactose free
50mcg tablet: £0.51
75mcg tablet: £2.80
100mcg tablet: £0.51
Liothyronine5mcg capsule: £55.00 NHS Somerset classify as amber as per traffic light guidance for NEW patients who have been accepted for trial and shown benefit as per Liothyronine shared care protocol. See NHS Somerset Shared Care and PGDs. Applies to Liothyronine CAPSULES only.
All other forms of liothyronine are non-formulary including Liothyronine tablets and unlicensed preparations such as Armour Thyroid.
10mcg capsule: £65.00
20mcg capsule: £55.00
Antithyroid drugs
Sulfur containing imidazolesCarbimazole5mg tablet: £2.61 (100)
20mg tablet: £3.75 (100)
ThiouracilsPropylthiouracil50mg tablet: £4.90 (56)