What are the symptoms of hypothyroidism (underactive thyroid)?

Medical Advisory BoardAll articles are reviewed for accuracy by our Medical Advisory Board
Educational purpose only • Exercise caution as content is pending human review
Article Review Status
Submitted
Under Review
Approved

Last updated: May 20, 2025View editorial policy

Personalize

Help us tailor your experience

Which best describes you? Your choice helps us use language that's most understandable for you.

From the Guidelines

Hypothyroidism symptoms include fatigue, feeling cold, weight gain, hair loss, and constipation, as noted in a study published in the Annals of Internal Medicine 1. These symptoms occur because the thyroid gland doesn't produce enough thyroid hormones, which are essential for regulating metabolism. When metabolism slows, many bodily functions are affected. Symptoms typically develop slowly over years, making them easy to miss or attribute to aging. Severe hypothyroidism, if left untreated, can progress to myxedema, a life-threatening condition characterized by intense cold intolerance, drowsiness, and unconsciousness. Some key points to consider about hypothyroidism symptoms include:

  • Fatigue and feeling cold are common symptoms, as reported in a study published in JAMA 1
  • Weight gain, hair loss, and constipation are also frequent complaints
  • Hypothyroidism is diagnosed through blood tests measuring thyroid-stimulating hormone (TSH) and thyroxine (T4) levels
  • Treatment usually involves daily oral medication with synthetic thyroid hormone levothyroxine, which restores adequate hormone levels and reverses symptoms
  • Regular blood tests are needed to monitor hormone levels and adjust medication dosage as necessary, as recommended by the USPSTF 1. It's essential to note that some individuals with subclinical hypothyroidism may experience symptoms compatible with hypothyroidism, and a trial of levothyroxine may be considered, as suggested in a study published in JAMA 1. However, the likelihood of improvement is small, and it must be balanced against the inconvenience, expense, and potential risks of therapy. The most critical consideration in managing hypothyroidism is to prioritize the patient's quality of life and prevent long-term complications, as emphasized in a study published in the Annals of Internal Medicine 1.

From the FDA Drug Label

6 ADVERSE REACTIONS Adverse reactions associated with levothyroxine sodium therapy are primarily those of hyperthyroidism due to therapeutic overdosage

The FDA drug label does not answer the question.

From the Research

Symptoms of Hypothyroidism

  • Fatigue, lethargy, and weight gain are common symptoms of hypothyroidism, as reported in studies 2, 3, 4, 5
  • Cold intolerance, constipation, and dry skin are also frequently observed symptoms 2, 3, 6, 4
  • Voice changes and bradycardia may also occur in some patients 3, 6, 4
  • Symptoms can range from minimal to life-threatening, with myxedema coma being a rare but severe complication 2, 4, 5

Variability in Symptoms

  • Symptoms of hypothyroidism can vary with age and sex, among other factors 3, 5
  • Subclinical hypothyroidism may not present with noticeable symptoms, despite elevated TSH levels 6, 4
  • Some patients may experience persistent symptoms despite normal thyroid function tests and levothyroxine treatment 3, 4, 5

Diagnosis and Treatment

  • Diagnosis of hypothyroidism is typically based on blood levels of thyroid-stimulating hormone and free thyroxine 2, 3, 4, 5
  • Levothyroxine replacement therapy is the standard treatment for hypothyroidism, with the goal of normalizing thyroid function tests 2, 3, 6, 4, 5

References

Guideline

Guideline Directed Topic Overview

Dr.Oracle Medical Advisory Board & Editors, 2025

Research

Hypothyroidism.

Lancet (London, England), 2017

Research

Hypothyroidism: Diagnosis and Treatment.

American family physician, 2021

Research

Hypothyroidism.

Lancet (London, England), 2024

Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

Have a follow-up question?

Our Medical A.I. is used by practicing medical doctors at top research institutions around the world. Ask any follow up question and get world-class guideline-backed answers instantly.