Patients with primary hypothyroidism usually present with non-specific symptoms of weakness, lethargy, depression, and mild weight gain.
Commonly, disease is sub-clinical.
Physical examination may show dry skin, thick tongue, eyelid oedema, and bradycardia.
Elevated thyroid-stimulating hormone and low free thyroxine confirms the diagnosis.
Treatment is with levothyroxine; starting dose depends on age and presence of co-existing cardiac disease.
Over-treatment is uncommon but can lead to iatrogenic hyperthyroidism.
Hypothyroidism is a clinical state resulting from underproduction of the thyroid hormones thyroxine (T4) and triiodothyronine (T3). Most cases are due to primary hypothyroidism, a failure of the thyroid gland to produce thyroid hormones. Primary hypothyroidism is defined as thyroid-stimulating hormone (TSH) concentrations above the reference range and free thyroxine concentrations below the reference range. Secondary hypothyroidism is due to underproduction of TSH by the pituitary gland. Sub-clinical hypothyroidism is a state of usually asymptomatic, mild thyroid failure, with normal levels of T4 and T3, and minimal elevation of TSH. Myxoedema coma is a rare severe form of hypothyroidism with multi-organ failure.
History and exam
Key diagnostic factors
- presence of risk factors
- non-specific symptoms
Other diagnostic factors
- weight gain
- menstrual irregularity
- dry or coarse skin
- change in voice
- delayed relaxation of tendon reflexes
- cold sensitivity
- coarse hair
- eyelid oedema
- iodine deficiency
- female sex
- middle age
- family history of autoimmune thyroiditis
- autoimmune disorders
- treatment for thyroid disease
- post-partum thyroiditis
- Turner's and Down's syndromes
- type 1 diabetes
- radiotherapy to head and neck
- infiltrative disease
- iodine excess
- amiodarone use
- lithium use
1st investigations to order
- serum thyroid-stimulating hormone (TSH)
Investigations to consider
- free serum T4
- antithyroid peroxidase antibodies
- fasting blood glucose
- serum cholesterol
confirmed overt primary hypothyroidism
sub-clinical hypothyroidism with TSH >10 mIU/L
- Central or secondary hypothyroidism
- Alzheimer's dementia
- Thyroid disease: assessment and management
- Asymptomatic thyroid dysfunction (2019)
Underactive thyroid: questions to ask your doctorMore Patient leaflets
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