Primary hypothyroidism

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Última revisão das evidências: 17 Feb 2026

Última atualização do tópico: 27 Feb 2026

Primary hypothyroidism usually presents with nonspecific symptoms of fatigue, depression, constipation, and mild weight gain; physical exam may show dry skin, eyelid edema, and bradycardia.

Elevated thyroid-stimulating hormone and low free thyroxine confirms diagnosis of overt primary hypothyroidism.

Commonly, disease is subclinical with minimal elevation of thyroid-stimulating hormone and normal thyroxine.

Treatment is with levothyroxine; starting dose depends on age and presence of coexisting cardiac disease.

Over-treatment is uncommon but can lead to iatrogenic hyperthyroidism.

Definição

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. Overt primary hypothyroidism is defined as thyroid-stimulating hormone (TSH) concentrations above the reference range and free thyroxine concentrations below the reference range.[1] Secondary hypothyroidism is due to underproduction of TSH by the pituitary gland.[2] Subclinical hypothyroidism is a state of mild thyroid failure, with normal levels of T4 and T3, and minimal elevation of TSH; it is usually asymptomatic.[3] Myxedema coma is a rare severe form of hypothyroidism that can lead to multiorgan failure.[2]

História e exame físico

Principais fatores diagnósticos

nonspecific symptoms

Detalhes completos

Outros fatores diagnósticos

lethargy
constipation
weight gain
depression
menstrual irregularity
dry or coarse skin
change in voice
bradycardia
hypertension
delayed relaxation of tendon reflexes
cold sensitivity
coarse hair
eyelid edema
goiter

Detalhes completos

Fatores de risco

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
exposure to pesticides
amiodarone use
lithium use
laryngectomy
treatment for multidrug-resistant tuberculosis (TB)

Detalhes completos

Investigações diagnósticas

Primeiras investigações a serem solicitadas

serum thyroid-stimulating hormone (TSH)

Detalhes completos

Tests to avoid

thyroid ultrasound

Detalhes completos

Investigações a serem consideradas

free serum thyroxine (T4)
antithyroid peroxidase antibodies (anti-TPOAbs)
CBC
fasting blood glucose
serum cholesterol

Detalhes completos

Algoritmo de tratamento

CONTÍNUA

confirmed overt primary hypothyroidism

subclinical hypothyroidism

Colaboradores

Autores

Wail Malaty, MD

Adjunct Clinical Professor

Department of Family Medicine

University of North Carolina

Chapel Hill

Declarações

WM declares that he has no competing interests.

Revisores

Sun Y. Lee, MD, MSc

Assistant Professor of Medicine

Boston University School of Medicine

Boston

Declarações

SYL declares that she has no competing interests.

Salman Razvi, MD, FRCP

Consultant Endocrinologist

Queen Elizabeth Hospital

Gateshead

Declarações

SR declares that he has no competing interests.

Lakdasa Premawardhana, MBBS, FRCP, FRCPE

Consultant Physician

Caerphilly Miners' Hospital

Caerphilly

Declarações

LP declares that he has no competing interests.

Birte Nygaard, MD, PhD

Associated Professor

Consultant Endocrinologist

Herlev Hospital

University of Copenhagen

Denmark

Declarações

BN declares that she has no competing interests.

Créditos aos pareceristas

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Declarações

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Referências

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Principais artigos

Taylor PN, Medici MM, Hubalewska-Dydejczyk A, et al. Hypothyroidism. Lancet. 2024 Oct 5;404(10460):1347-64. Resumo

Alexander EK, Pearce EN, Brent GA, et al. 2017 guidelines of the American Thyroid Association for the diagnosis and management of thyroid disease during pregnancy and the postpartum. Thyroid. 2017 Mar;27(3):315-89.Texto completo Resumo

American Association of Clinical Endocrinologists; American Thyroid Association. Clinical practice guidelines for hypothyroidism in adults: cosponsored by the American Association of Clinical Endocrinologists and the American Thyroid Association. Endocr Pract. 2012 Nov-Dec;18(6):988-1028.Texto completo Resumo

Jonklaas J, Bianco AC, Bauer AJ, et al. Guidelines for the treatment of hypothyroidism: prepared by the American Thyroid Association Task Force on Thyroid Hormone Replacement. Thyroid. 2014 Dec;24(12):1670-751.Texto completo Resumo

Artigos de referência

Uma lista completa das fontes referenciadas neste tópico está disponível para os usuários com acesso total ao BMJ Best Practice.

Differentials
- Central or secondary hypothyroidism
- Depression
- Alzheimer dementia
More Differentials
Guidelines
- Thyroid function testing in the diagnosis and monitoring of thyroid function disorder
- Thyroid disease in pregnancy
More Guidelines
Patient information
Underactive thyroid
Underactive thyroid: questions to ask your doctor
More Patient information
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Primary hypothyroidism

Resumo

Definição

História e exame físico

Principais fatores diagnósticos

Outros fatores diagnósticos

Fatores de risco

Investigações diagnósticas

Primeiras investigações a serem solicitadas

Tests to avoid

Investigações a serem consideradas

Algoritmo de tratamento

confirmed overt primary hypothyroidism

subclinical hypothyroidism

Colaboradores

Autores

Wail Malaty, MD

Declarações

Revisores

Sun Y. Lee, MD, MSc

Declarações

Salman Razvi, MD, FRCP

Declarações

Lakdasa Premawardhana, MBBS, FRCP, FRCPE

Declarações

Birte Nygaard, MD, PhD

Declarações

Créditos aos pareceristas

Declarações

Referências

Principais artigos

Artigos de referência

Uma lista completa das fontes referenciadas neste tópico está disponível para os usuários com acesso total ao BMJ Best Practice.

Differentials

Guidelines

Patient information

Log in or subscribe to access all of BMJ Best Practice

Log in or subscribe to access all of BMJ Best Practice

Log in to access all of BMJ Best Practice