Table of contents
Expand All Topics
Hypothyroidism
Background
Overview
Definition
Hypothyroidism is a chronic endocrine disease associated with the deficiency of thyroxine and T3 thyroid hormones.
1
Pathophysiology
Hypothyroidism is most frequently caused by a failure of the thyroid gland to produce thyroid hormones (99%). Other causes include the underproduction of TSH by the pituitary gland and deficiency of the thyrotropin-releasing hormone.
1
Epidemiology
The prevalence of overt and subclinical hypothyroidism in the US is estimated at 300 per 100,000 population and 4,300 per 100,000 population, respectively. Hypothyroidism is 2-8 times more prevalent in women than men, and it's prevalence increases with age.
1
Disease course
Clinical manifestations include weight gain, fatigue, proximal weakness, decreased concentration, depression, diffuse muscle pain, menstrual irregularities, constipation, dry skin, hair loss, and sensory neuropathy. A severe form of hypothyroidism-myxedema coma- presents with altered mental status, hypothermia, hyponatremia and bradycardia. The disease decreases productivity and QoL.
1
Prognosis and risk of recurrence
Hypothyroidism is not associated with an increase in mortality. Treatment is well tolerated and results in improved QoL in most patients. However, untreated hypothyroidism leads to disease progression and ultimately, coma and death.
2
Guidelines
Key sources
The following summarized guidelines for the evaluation and management of hypothyroidism are prepared by our editorial team based on guidelines from the European Thyroid Association (ETA 2025), the American College of Obstetricians and Gynecologists (ACOG 2020), the Endocrine Society (ES 2020), the American Heart Association (AHA/HRS/ACC 2019), the American Thyroid Association (ATA 2017), and the American Thyroid Association (ATA/AACE 2012).
1
2
3
4
5
6
7
8
Screening and diagnosis
Clinical scoring systems: as per AACE/ATA 2012 guidelines, avoid using clinical scoring systems to diagnose hypothyroidism.
D
More topics in this section
Indications for screening
Indications for testing (dyslipidemia)
Indications for testing (infertility)
Diagnostic investigations
Anti-TPO antibodies: as per AACE/ATA 2012 guidelines, measure anti-TPO antibodies in the evaluation of patients with subclinical hypothyroidism.
B
Show 3 more
More topics in this section
Thyroid hormone tests
Other diagnostic tests
Medical management
Levothyroxine therapy, indications, abnormal TSH
As per AACE/ATA 2012 guidelines:
Consider initiating levothyroxine in patients with serum TSH levels > 10 mIU/L, as these patients are at increased risk for HF and cardiovascular mortality.
B
Consider initiating treatment based on individual factors in patients with TSH levels between the upper limit of a given laboratory's reference range and 10 mIU/L, particularly if patients have symptoms suggestive of hypothyroidism, positive anti-TPO antibodies, or evidence of ASCVD, HF, or associated risk factors for these diseases.
B
More topics in this section
Levothyroxine therapy (indications, normal TSH)
Levothyroxine therapy (choice of agent)
Levothyroxine therapy (formulations)
Levothyroxine therapy (timing of dosing)
Levothyroxine therapy (initial dosing)
Levothyroxine therapy (maintenance dosing)
Levothyroxine therapy (treatment targets)
Management of dyslipidemia
Nonpharmacologic interventions
Iodine supplementation: as per AACE/ATA 2012 guidelines, do not use iodine supplementation, including kelp or other iodine-containing functional foods, in the management of hypothyroidism in iodine-sufficient areas.
D
More topics in this section
Nutraceuticals
Selenium supplementation
Specific circumstances
Pregnant patients, screening
As per ACOG 2020 guidelines:
Do not obtain universal screening for thyroid disease in pregnancy because identification and treatment of maternal subclinical hypothyroidism has not been shown to result in improved pregnancy outcomes and neurocognitive function in offspring.
D
Obtain TSH as a first-line screening test to assess thyroid status if indicated.
A
More topics in this section
Pregnant patients (testing)
Pregnant patients (management)
Pregnant patients (monitoring)
Patients undergoing fertility treatment
Patients with comorbidities
Patients with combined adrenal insufficiency
Follow-up and surveillance
Assessment of treatment adherence
As per ETA 2025 guidelines:
Explore low adherence to treatment or pseudomalabsorption when the dose of levothyroxine required to restore serum TSH within the reference interval exceeds 1.5-1.7 mcg/kg/day in adult hypothyroid patients with thyroid in situ or 1.8-2.0 mcg/kg/day in a thyroidectomized patient.
B
Obtain a levothyroxine absorption test in levothyroxine refractory patients, after excluding nutrients, drugs, and known interference from comorbidities, when clinically appropriate.
B
More topics in this section
TSH monitoring
Indications for specialist referral