Suspected hypothyroidism (adults)
Tiredness, cold intolerance, constipation, weight gain, dry skin. For adults. Not for children.
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Hypothyroidism Management (ATA Guidelines)
Hypothyroidism Management (ATA Guidelines): Suspected hypothyroidism (adults) → Red flag: myxoedema coma is an emergency → Pregnant or planning pregnanc...
Pathway Overview
19 steps
Algorithm Steps
19 total
01Start 02Warning Red flag: myxoedema coma is an emergency
Reduced consciousness, hypothermia, slow heart rate, low BP, hypoventilation or low sodium. Do not use this outpatient pathway.
- Transfer to ED or ICU now; outside hospital call 000
- IV glucocorticoid first, then IV levothyroxine, with ICU and endocrinology
- Start treatment on clinical suspicion; do not wait for results
03Warning Pregnant or planning pregnancy: different targets
Overt hypothyroidism found in pregnancy: start levothyroxine now and arrange obstetric and endocrine care. Use trimester-specific TSH ranges.
- Already on levothyroxine: add 2 extra doses a week (about 30% more) as soon as pregnancy is confirmed
- Check TSH every 4 weeks in the first half of pregnancy, and again later in pregnancy
- Planning pregnancy on levothyroxine: aim for TSH below 2.5 mIU/L before conception
04Action Test TSH first
TSH alone is the first test when pituitary disease is not suspected.
- TSH above range: measure free T4 on the same sample
- Pituitary or hypothalamic disease known or suspected: measure TSH and free T4 together
- Do not test during acute illness unless thyroid disease may be the cause
- Ask about biotin supplements: they can give false results
05Decision Classify the TSH and free T4 result
Each next step states the result it applies to.
- High TSH, low free T4: overt primary hypothyroidism
- High TSH, normal free T4: subclinical hypothyroidism
- Low free T4 with low or normal TSH: possible central hypothyroidism
- Normal TSH: primary hypothyroidism excluded
- Low TSH, normal or high free T4: assess for hyperthyroidism
- High free T4 with normal or high TSH: check for assay interference; endocrinology
- High TSH, low FT4
06Warning High TSH, low FT4: first exclude adrenal insufficiency and acute cardiac disease
Levothyroxine given before glucocorticoid can precipitate adrenal crisis.
- Suspect adrenal insufficiency in pituitary disease, Addison disease, autoimmune polyglandular disease, or low BP, low sodium or high potassium
- Check morning cortisol; if adrenal insufficiency is likely, start glucocorticoid before levothyroxine
- Acute myocardial infarction or acute myocarditis: seek specialist advice before levothyroxine
07Action Overt hypothyroidism: start levothyroxine
Adults, not pregnant. Known coronary disease: start 12.5-25 mcg/day and increase slowly.
- Adults under 65 with no cardiovascular disease: 1.6 mcg/kg/day (round to nearest 25 mcg; in marked obesity use ideal body weight; usual adult dose 100-200 mcg/day)
- Age 65 or over, or cardiovascular disease: start 25-50 mcg/day and titrate
- Known coronary disease or angina: start 12.5-25 mcg/day
- Take 60 min before breakfast or at bedtime (3 h after food), same time daily
08Action Titrate levothyroxine
Adjust by 12.5-25 mcg/day. Recheck TSH 4-6 weeks after each change. On warfarin: check INR after each dose change.
- Keep the same brand; if the brand changes, check TSH and free T4 after 6 weeks
- Separate from calcium and iron by about 4 hours
- Need rises with PPIs, sucralfate, sevelamer, soy, oestrogen, and enzyme inducers (carbamazepine, phenytoin, rifampicin)
- Eutroxsig and Oroxine: store in the fridge (2-8 °C); the strip in use can stay below 25 °C for up to 14 days
09Action Monitoring on levothyroxine
Check TSH 4-6 weeks after each dose or brand change. Central hypothyroidism: use free T4, not TSH. The next step depends on the TSH.
- Target: TSH within the reference range
- Age over 70-80: TSH 4-6 mIU/L is a reasonable target
- A very high starting TSH can take up to 6 months to normalise
- Once stable: TSH at 4-6 months, then yearly
- TSH above target
10Action TSH above target: find the cause, then increase
In a previously stable patient, repeat the test before a dose change.
- Check adherence and timing with food
- Check interacting drugs and supplements (calcium, iron, PPIs)
- Consider malabsorption: coeliac disease, atrophic gastritis, H. pylori, bowel surgery
- Increase by 12.5-25 mcg/day; recheck TSH in 4-6 weeks
- Path rejoins step 09Shared downstream outcome
- TSH at target
11Outcome TSH at target: continue the same dose
TSH yearly. Recheck after weight change, pregnancy, a new interacting drug or a brand change.
- Dose need falls with age and weight loss
- Dose need rises with pregnancy and weight gain
- TSH below target
12Warning TSH below target: reduce the dose
Over-replacement raises the risk of AF and osteoporosis, most with TSH below 0.1 mIU/L, in older adults and after menopause.
- Thyroid cancer or central hypothyroidism: follow specialist targets; do not reduce on TSH alone
- Otherwise reduce by 12.5-25 mcg/day
- Recheck TSH in 4-6 weeks
- Path rejoins step 09Shared downstream outcome
- High TSH, normal FT4
13Decision High TSH, normal free T4 (subclinical): treat?
Repeat TSH and free T4 after 3 months before deciding. Consider TPO antibodies once.
- Consider treatment: TSH 10 mIU/L or higher on 2 tests 3 months apart
- Consider a 6-month trial: under 65, with symptoms, TSH above range but below 10 on 2 tests
- Age 65 or over with TSH below 10: treatment gave no benefit; usually do not treat
- Pregnant or planning pregnancy: obstetric and endocrine care
- If Yes
- Treat
14Action Subclinical, treatment chosen: low-dose levothyroxine
Start 25-50 mcg/day; coronary disease 12.5-25 mcg/day. Not routine at age 65 or over with TSH below 10.
- Possible adrenal insufficiency: check cortisol before levothyroxine
- Recheck TSH in 4-6 weeks; target TSH within the reference range
- Symptoms persist with TSH in range: consider stopping
- Path rejoins step 09Shared downstream outcome
If No- Observe
15Action Subclinical, not treated: monitor
No levothyroxine now. Reassess if TSH reaches 10 mIU/L, free T4 falls or symptoms develop.
- TSH and free T4 yearly if TPO antibodies are raised or after thyroid surgery or radioiodine
- Otherwise TSH and free T4 every 2-3 years
- Path rejoins step 13Shared downstream outcome
- Low FT4, low or normal TSH
16Action Low free T4 with low or normal TSH: possible central hypothyroidism
Refer to endocrinology. Exclude adrenal insufficiency before levothyroxine.
- Assess other pituitary hormones and pituitary imaging with endocrinology
- Adrenal insufficiency: start glucocorticoid before levothyroxine
- On treatment, dose by free T4 (upper half of reference range), not TSH
- Severe non-thyroidal illness can cause the same pattern
- Normal TSH
17Outcome Normal TSH: primary hypothyroidism excluded
Look for other causes of the symptoms. Known pituitary disease: check free T4.
- Consider non-thyroid causes
- Pituitary or hypothalamic disease: a normal TSH does not exclude central hypothyroidism
- Low TSH
18Outcome Low TSH with normal or high free T4: not hypothyroidism
Measure free T3 and assess for hyperthyroidism. Low TSH with low free T4: follow the central hypothyroidism step.
- High FT4, TSH not suppressed
19Outcome High free T4 with normal or high TSH: do not start levothyroxine; refer
Repeat on another assay and ask about biotin and recently resumed levothyroxine. Causes include assay interference, TSH-secreting pituitary tumour and thyroid hormone resistance. Refer to endocrinology.
Guideline Source
Guidelines for the Treatment of Hypothyroidism (American Thyroid Association Task Force on Thyroid Hormone Replacement), Thyroid 2014
Clinical Safety Information
Clinical Decision Support — Not a Substitute for Clinical Judgment
Individual patient factors may require deviation from these recommendations.
Known Limitations
- For non-pregnant adults. Not for children or myxoedema coma.
- Central hypothyroidism and thyroid cancer need specialist targets; this pathway does not set them.
- Pregnancy is flagged only; follow ATA 2017 pregnancy guidance with obstetric and endocrine care.
- Subclinical treatment advice is based on NICE NG145 and the TRUST trial; evidence for benefit is limited.
- Dosing must be individualised to age, weight, cardiac status and interacting drugs.
Contraindicated Populations
Children and adolescents (weight-based paediatric dosing)Suspected myxoedema coma (emergency care)Pregnancy (use pregnancy-specific thyroid care)
Applicable Regions
USEUUKAU
AU: Australian PI (Eutroxsig, Oroxine): do not interchange levothyroxine brands; if switched, monitor TSH. Store in the fridge (2-8 °C). Uncorrected adrenal insufficiency is a contraindication.
EU: Consistent with ETA 2025 guideline on levothyroxine preparations (same brand; retest 6 weeks after a switch).
UK: Subclinical treatment and monitoring follow NICE NG145 (2019, updated 2023).
US: Based on ATA 2014 hypothyroidism treatment guideline.
Version 2Next review: 2027-09-30
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Related Resources
Frequently Asked Questions
What is the Hypothyroidism Management (ATA Guidelines)?
The Hypothyroidism Management (ATA Guidelines) is a management clinical algorithm for Internal Medicine. It provides a structured decision tree to guide clinical decision-making, based on Guidelines for the Treatment of Hypothyroidism (American Thyroid Association Task Force on Thyroid Hormone Replacement), Thyroid 2014.
What guideline is the Hypothyroidism Management (ATA Guidelines) based on?
This algorithm is based on Guidelines for the Treatment of Hypothyroidism (American Thyroid Association Task Force on Thyroid Hormone Replacement), Thyroid 2014 (DOI: 10.1089/thy.2014.0028).
What are the limitations of the Hypothyroidism Management (ATA Guidelines)?
Known limitations include: For non-pregnant adults. Not for children or myxoedema coma.; Central hypothyroidism and thyroid cancer need specialist targets; this pathway does not set them.; Pregnancy is flagged only; follow ATA 2017 pregnancy guidance with obstetric and endocrine care.; Subclinical treatment advice is based on NICE NG145 and the TRUST trial; evidence for benefit is limited.; Dosing must be individualised to age, weight, cardiac status and interacting drugs.. Individual patient factors may require deviation from these recommendations.
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