Treatment algorithm

Please note that formulations/routes and doses may differ between drug names and brands, drug formularies, or locations. Treatment recommendations are specific to patient groups: see disclaimer

ONGOING

confirmed overt primary hypothyroidism

1st line – levothyroxine

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ONGOING
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confirmed overt primary hypothyroidism
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healthy with age ≤65 years
1st line – 

levothyroxine

The goal of treatment is reduction of symptoms and prevention of long-term complications.[1][8] Treatment is given upon establishing the diagnosis and is lifelong.

Patients should be started on the full replacement dose of levothyroxine.[1][42][46]

The main complication of treatment is over-replacement of thyroid hormone, which increases the risk of osteoporosis and atrial fibrillation.[1]

Pregnancy increases thyroid hormone requirements and the required dose of levothyroxine may increase. Thyroid-stimulating hormone (TSH) should be measured every 4-6 weeks in pregnant women on levothyroxine therapy until mid-gestation, then once in each of the second and third trimesters.​[29][47]​ It may be necessary to increase the dose of levothyroxine by 25% to 30% in the first trimester of pregnancy.[29] Nephrotic syndrome and malabsorption (e.g., coeliac disease) can increase levothyroxine requirements.[1][42]​ Concomitant use of iron, cholestyramine, calcium, sucralfate, anticonvulsants (e.g., phenytoin, phenobarbital, and carbamazepine), rifampin, and sertraline may cause an increase in dosage requirements.[1][8]

The dose is adjusted in small increments to normalise TSH, which is the chemical goal of therapy. Due to the long half-life of levothyroxine (1 week), TSH should be measured 4-6 weeks after initiation of therapy or dosage change.[8][42]

Primary options

levothyroxine: 1.6 micrograms/kg/day orally adjust dose in increments of 12.5 to 25 micrograms to normalise TSH

1st line – low-dose levothyroxine

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ONGOING
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confirmed overt primary hypothyroidism
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pre-existing coronary artery disease or age >65 years
1st line – 

low-dose levothyroxine

Levothyroxine therapy may exacerbate angina in patients with coronary artery disease.[42] A lower starting dose of levothyroxine is recommended, with titration in small increments every 4-6 weeks to a full therapeutic dose and close attention to the development of ischaemic symptoms.[42] Patients aged over 65 years even without heart disease are also less tolerant of full replacement initial doses.[42] A low starting dose is recommended in these patients with titration in small increments every 4-6 weeks.

The goal of treatment is reduction of symptoms and prevention of long-term complications.[1][8] Treatment is given upon establishing the diagnosis and is lifelong.

The main complication of treatment is over-replacement of thyroid hormone, which increases the risk of osteoporosis and atrial fibrillation.[1]

Nephrotic syndrome and malabsorption (e.g., coeliac disease) can increase levothyroxine requirements.[1][42] Concomitant use of iron, cholestyramine, calcium, sucralfate, anticonvulsants (e.g., phenytoin, phenobarbital, and carbamazepine), rifampin, and sertraline may cause an increase in dosage requirements.[1][8]

The dose is adjusted in small increments to normalise thyroid-stimulating hormone (TSH), which is the chemical goal of therapy. Due to the long half-life of levothyroxine (1 week), TSH should be measured 4-6 weeks after initiation of therapy or dosage change.[8][42]

Primary options

levothyroxine: 25-50 micrograms orally once daily, adjust dose in increments of 12.5 to 25 micrograms every 4-6 weeks

sub-clinical hypothyroidism with TSH >10 mIU/L

1st line – low-dose levothyroxine

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ONGOING
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sub-clinical hypothyroidism with TSH >10 mIU/L
1st line – 

low-dose levothyroxine

In cases where the thyroid-stimulating hormone (TSH) is only mildly raised, the patient is not symptomatic and the serum free thyroxine (T4) is normal, the diagnosis is sub-clinical hypothyroidism.[2] Many experts recommend treating if TSH is >10 mIU/L, as the theoretical risk of progression to overt hypothyroidism is high.[2][8][43]​ There is also some evidence that there is an increased risk of coronary heart disease.[44] Despite the lack of good evidence, some experts recommend treating adults aged under 70 years (who have goitre, antithyroid peroxidase antibodies, or symptoms of hypothyroidism) with sub-clinical hypothyroidism and TSH <10 mIU/L.[45]

Treatment is recommended for pregnant women if the TSH is greater than the pregnancy-specific reference range and they are thyroid peroxidase antibody (TPOAb) positive. If they are TPOAb negative, treatment is recommended if the TSH is >10 mlU/L.[29]

Patients should be started on a low dose of levothyroxine. The dose is adjusted in small increments to normalise TSH, which is the chemical goal of therapy. Due to the long half-life of levothyroxine (1 week), TSH should be measured 4-6 weeks after initiation of therapy or dosage change.[8]

The main complication of treatment is over-replacement of thyroid hormone, which increases the risk of osteoporosis and atrial fibrillation.[1]

Pregnancy increases thyroid hormone requirements and the required dose of levothyroxine may increase. TSH should be measured every 4-6 weeks in pregnant women on levothyroxine therapy until mid-gestation, then once in each of the second and third trimesters.​[29][47]​​ It may be necessary to increase the dose of levothyroxine by 25% to 30% in the first trimester of pregnancy.[29] Nephrotic syndrome and malabsorption (e.g., coeliac disease) can increase levothyroxine requirements.[1][8]​​ Concomitant use of iron, cholestyramine, calcium, sucralfate, anticonvulsants (e.g., phenytoin, phenobarbital, and carbamazepine), rifampin, and sertraline may cause an increase in dosage requirements.[1][8]

Primary options

levothyroxine: 1 microgram/kg/day orally (usual dose 50-75 micrograms/day), adjust dose in increments of 25 to 50 micrograms to normalise TSH

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Please note that formulations/routes and doses may differ between drug names and brands, drug formularies, or locations. Treatment recommendations are specific to patient groups. See disclaimer

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