management

Last edited 12/2019 and last reviewed 06/2021

Treatment of subclinical hyperthyroidism is controversial (1).

  • some authorities suggest it is better to treat subclinical hypothyroidism before overt hypothyroidism develops, especially in patients with positive thyroid antibodies as the rate of progression to overt hypothyroidism is much higher in these patients

NICE suggest (2):

Tests for people with confirmed subclinical hypothyroidism

Adults

Consider measuring thyroid peroxidase antibodies (TPOAbs) for adults with TSH levels above the reference range, but do not repeat TPOAbs testing.

Treating subclinical hypothyroidism

When discussing whether or not to start treatment for subclinical hypothyroidism, take into account features that might suggest underlying thyroid disease, such as symptoms of hypothyroidism, previous radioactive iodine treatment or thyroid surgery, or raised levels of thyroid autoantibodies.

Adults

Consider levothyroxine for adults with subclinical hypothyroidism who have a TSH of 10 mlU/litre or higher on 2 separate occasions 3 months apart.

Consider a 6-month trial of levothyroxine for adults under 65 with subclinical hypothyroidism who have:

  • a TSH above the reference range but lower than 10 mlU/litre on 2 separate occasions 3months apart,
  • and symptoms of hypothyroidism.

If symptoms do not improve after starting levothyroxine, re-measure TSH and if the level remains raised, adjust the dose. If symptoms persist when serum TSH is within the reference range, consider stopping levothyroxine and follow the recommendations on monitoring untreated subclinical hypothyroidism and monitoring after stopping treatment.

Children and young people aged 2 years and over

Consider levothyroxine for children aged 2 years and over and young people with subclinical hypothyroidism who have:

  • a TSH level of 20mlU/litre or higher, or
  • a TSH level between 10 and 20mlU/litre on 2 separate occasions 3months apart,
  • or a TSH level between 5 and 10 mlU/litre on 2 separate occasions 3 months apart, and thyroid dysgenesis (an underdeveloped thyroid gland),
  • or signs or symptoms of thyroid dysfunction.

Children under 2 years

Consider levothyroxine for children aged between 28 days and 2 years with subclinical hypothyroidism who have a TSH level of 10 mlU/litre or higher.

 

Increased TSH may be transient and may reflect a non-thyroidal illness or transient thyroiditis from which the patient is recovering (1)

  • do not start treatment on the basis of a single raised TSH level in people who are antibody negative (3,4)

In patients with normal serum free T4 levels and thyroid stimulating hormone (TSH) level above the reference range but 10 mU/L or less in the initial test:

  • confirmation of the results should be done by repeating the thyroid function testing along with thyroid peroxidase antibodies within 3-6 months of the initial test (1,5)
  • levothyroxine is not recommended as a routine therapy
  • thyroxine may be considered in patients with a goitre, in pregnancy and in patients with rising TSH levels (5)
  • a therapeutic trial of levothyroxine can be considered in patients with increased TSH and symptoms consistent with hypothyroidism
    • treatment should be carried out for three to six months in order to judge whether there is symptomatic benefit
    • treatment can be continued in patients with a clear improvement in symptoms
  • treatment may be deferred in
    • patients with thyroid peroxidase antibodies, stable hormone levels but without any symptoms of hypothyroidism
      • risk of progression to overt hypothyroidism is less than 5% per year
      • yearly surveillance of the TSH level is recommended (or earlier if symptoms develop) (1)
    • patients without antithyroid antibodies (thyroid peroxidase autoantibodies)
      • conversion rate to overt hypothyroidism is less than 3% per year (3)
      • repeat measurement of serum TSH approximately every three years is recommended (or earlier if symptoms develop) (1)

In patients with a normal serum free T4 level and thyroid-stimulating hormone (TSH) level greater than 10 mU/L in the initial test:

  • confirmation of the results should be done by repeating the thyroid function testing within 3-6 months of the initial test (1,5)
  • treatment with thyroxine is recommended sincethere is an increase risk of progression to overt hypothyroidism and deterioration in hyperlipidaemia with time (in patients with elevated thyroid peroxidase autoantibodies) (5)

The aim of treatment is to restore serum TSH concentration to within the reference range; levels below this range may be associated with an increased risk of developing atrial fibrillation. However overall, the risks of thyroxine therapy are probably minimal provided the TSH is kept within the normal range, and a trial of treatment in symptomatic patients with subclinical hypothyroidism may be acceptable (4)

  • if thyroxine therapy is initiated then a usual starting dose would be 50-100 mcg per day (although 25 mcg per day may be sufficient)
    • 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
      • (2)
  • start with 25 mcg daily and increase cautiously if coexistent heart disease or the elderly (6)

Reference:

Related pages:

monitoring thyroxine (levothyroxine) therapy

monitoring untreated subclinical hypothyroidism after stopping treatment