Patients with primary hypothyroidism usually present with nonspecific symptoms of weakness, lethargy, depression, and mild weight gain.
Commonly, disease is subclinical.
Physical exam may show dry skin, thick tongue, eyelid edema, 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. Subclinical hypothyroidism is a state of usually asymptomatic, mild thyroid failure, with normal levels of T4 and T3, and minimal elevation of TSH. Myxedema coma is a rare severe form of hypothyroidism with multiorgan failure.
History and exam
Key diagnostic factors
- nonspecific 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 edema
- iodine deficiency
- female sex
- middle age
- family history of autoimmune thyroiditis
- autoimmune disorders
- treatment for thyroid disease
- postpartum thyroiditis
- Turner and Down syndromes
- type 1 diabetes
- radiation therapy 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
subclinical hypothyroidism with TSH >10 mIU/L
- Central or secondary hypothyroidism
- Alzheimer dementia
- Asymptomatic thyroid dysfunction (2019)
- Thyroid disease: assessment and management
Underactive thyroid: questions to ask your doctorMore Patient leaflets
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