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).14 Central causes, such as low levels of thyroid-stimulating hormone (TSH) and free thyroxine (FT4), are rare.

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SORT: KEY RECOMMENDATIONS FOR PRACTICE

Clinical recommendationEvidence ratingComments

Screening for thyroid dysfunction in nonpregnant, asymptomatic adults has uncertain risks and benefits.13

C

No studies have directly compared the benefits and harms of screening vs. no screening

Patients with hypothyroidism should not be treated with triiodothyronine, alone or in combination with levothyroxine.5,26

A

Evidence-based guidelines generated from consistent, prospective, randomized trials

Patients with hypothyroidism should not be treated with iodine supplementation unless they are from an area with known iodine insufficiency.5

B

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

C

Consensus, expert opinion

In women with controlled hypothyroidism who become pregnant, the levothyroxine dosage should be increased by 30%, from seven to nine doses per week, with the thyroid-stimulating hormone level checked every four weeks.22,23

A

Consistent high-quality randomized trials

Nonpregnant patients with subclinical hypothyroidism should not be treated with thyroid hormone therapy unless the thyroid-stimulating hormone level is greater than 10 mIU per L or the thyroid peroxidase antibody is elevated.16,17,34

A

Consistent, prospective, randomized data and meta-analysis


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.

The Authors

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STEPHEN A. WILSON, MD, MPH, FAAFP, is the chair of and a professor in the Department of Family Medicine at Boston (Mass.) University School of Medicine. At the time this article was initiated, he was the executive vice chair of the Department of Family Medicine at the University of Pittsburgh (Pa.)....

LEAH A. STEM, MD, MS, is a faculty member at the University of Pittsburgh Medical Center St. Margaret Family Medicine Residency Program.

RICHARD D. BRUEHLMAN, MD, is the director of Community Preceptors and a faculty member at the University of Pittsburgh Medical Center St. Margaret Family Medicine Residency Program.

Address correspondence to Stephen A. Wilson, MD, MPH, Boston Medical Center, 1 Boston Medical Center Pl., Dowling 5, Room 5309, Boston, MA 02118 (email: stephen.wilson@bmc.org). Reprints are not available from the authors.

Author disclosure: No relevant financial affiliations.

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