Hypothyroidism: Diagnosis and Treatment
Am Fam Physician. 2021 May 15;103(10):605-613.
Patient information: A handout on this topic is available at https://familydoctor.org/condition/hypothyroidism/.
Clinical hypothyroidism affects one in 300 people in the United States, with a higher prevalence among female and older patients. Symptoms range from minimal to life-threatening (myxedema coma); more common symptoms include cold intolerance, fatigue, weight gain, dry skin, constipation, and voice changes. The signs and symptoms that suggest thyroid dysfunction are nonspecific and nondiagnostic, especially early in disease presentation; therefore, a diagnosis is based on blood levels of thyroid-stimulating hormone and free thyroxine. There is no evidence that population screening is beneficial. Symptom relief and normalized thyroid-stimulating hormone levels are achieved with levothyroxine replacement therapy, started at 1.5 to 1.8 mcg per kg per day. Adding triiodothyronine is not recommended, even in patients with persistent symptoms and normal levels of thyroid-stimulating hormone. Patients older than 60 years or with known or suspected ischemic heart disease should start at a lower dosage of levothyroxine (12.5 to 50 mcg per day). Women with hypothyroidism who become pregnant should increase their weekly dosage by 30% up to nine doses per week (i.e., take one extra dose twice per week), followed by monthly evaluation and management. Patients with persistent symptoms after adequate levothyroxine dosing should be reassessed for other causes or the need for referral. Early recognition of myxedema coma and appropriate treatment is essential. Most patients with subclinical hypothyroidism do not benefit from treatment unless the thyroid-stimulating hormone level is greater than 10 mIU per L or the thyroid peroxidase antibody is elevated.
Hypothyroidism occurs when there is inadequate thyroid hormone production by the thyroid gland or insufficient stimulation by the hypothalamus or pituitary gland. Causes may include primary gland failure or can be iatrogenic, transient, or central (Table 1).1–4 Central causes, such as low levels of thyroid-stimulating hormone (TSH) and free thyroxine (FT4), are rare.
SORT: KEY RECOMMENDATIONS FOR PRACTICE
A = consistent, good-quality patient-oriented evidence; B = inconsistent or limited-quality patient-oriented evidence; C = consensus, disease-oriented evidence, usual practice, expert opinion, or case series. For information about the SORT evidence rating system, go to https://www.aafp.org/afpsort.
SORT: KEY RECOMMENDATIONS FOR PRACTICE
|Clinical recommendation||Evidence rating||Comments|
No studies have directly compared the benefits and harms of screening vs. no screening
Evidence-based guidelines generated from consistent, prospective, randomized trials
Patient-oriented evidence from nonprospective studies and consensus evaluation of those data
In newly diagnosed patients with hypothyroidism who are older than 60 years or with known or suspected ischemic heart disease, levothyroxine therapy should be initiated at 12.5 to 50 mcg per day.2,3,5,21
Consensus, expert opinion
Referencesshow all references
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