Spontaneous recovery in these patients is unlikely except when the hypothyroidism is drug induced hypothyroidism (for example, lithium, amiodarone, interferons) or if in the recovery phase of a thyroiditis (for example, postpartum thyroiditis or painful subacute thyroiditis) (1)
Symptomatic people with TSH levels above 10 mU/l should be started on treatment.
- confirm the increase in serum TSH on a second sample since treatment is likely to be life long (1)
Aim of treatment is to restore normal thyroid hormone concentration and to provide symptomatic relief for the patients (2)
- a full replacement dose of levothyroxine (1.6 µg/kg daily) should be started since titration of the dose upward from a low starting dose is unnecessary for most patients (1,2) (see notes) e.g. - 100 µg for a 60 kg woman and 125 µg for a 75 kg man
- patients over 60 years or with a history of ischaemic heart disease should receive a low dose (25-50 µg daily) and then titrate the dose upwards (1)
Thyroid function test should be done at least after 6-8 weeks of therapy.
- fine tuning of the dose could be necessary in some patients
- aim of levothyroxine treatment is to make the patient feel better, and the dose should be adjusted to maintain the level of thyroid stimulating hormone within the lower half of the reference range, around 0.4 to 2.5 mU/l. If the patient feels perfectly well with a level in the upper half of the reference range, then adjustment is unnecessary (1)
- TSH level below the reference range may be acceptable in younger patients who require a higher dose of levothyroxine to fully control symptoms but over treatment should be avoided (3)
- maintaining TSH concentrations below 0.1 mU/l is poor practice due to the increased risk of osteoporosis and atrial fibrillation. The exception to this is after thyroidectomy for thyroid cancer, when TSH values may need to be suppressed to and maintained at a concentration <0.1 mU/l (1)
Combination treatment with T3 and T4 is not recommended (3)
NICE suggest that (4):
- 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 longterm adverse effects are 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.
Notes:
- a small randomised controlled crossover trial has revealed that taking levothyroxine once a week (seven times the daily dose taken once weekly) is a safe regimen and may be effective in refractory cases (1)
- a randomized controlled trial has shown that the low starting dose regimen of levothyroxine is not required for most patients (except in patients aged 60 years or more and those with cardiac history) and a full replacement dose of levothyroxine is safe and may be more convenient and cost-effective (2)
- a combination of T4 and T3 has not been shown to have any advantage when compared with standard T4 monotherapy. Furthermore T3 is five times more active than T4 hence there is a risk of over treatment if the dose of T3 is not carefully controlled. Therefore addition of T3 in any form is not recommended (3)
Reference: