Underactive thyroid (hypothyroidism)

Also known as: Hypothyroidism, Sluggish Thyroid, Low Thyroid, Slow Metabolism Thyroid Disease, Thyroid Hormone Deficiency, Tired Thyroid

Last Updated: October 31, 2026

Key Points

Thyroid gland doesn't make enough hormones
Causes tiredness, weight gain, and feeling cold
Usually treated with daily hormone replacement medication
Symptoms develop slowly and worsen over time

Overview

Underactive thyroid, or hypothyroidism, is a common condition where the thyroid gland in your neck does not produce enough essential hormones. These hormones are vital for regulating your body's metabolism and energy levels. When hormone levels are low, various bodily functions can slow down. The most common cause in many regions is an autoimmune condition called Hashimoto's disease, where the immune system mistakenly attacks the thyroid. Other causes include previous thyroid surgery, radiation treatment, or certain medications. While symptoms can be subtle at first, they tend to worsen over time if untreated. Hypothyroidism is typically managed with daily hormone replacement medication, which helps restore normal hormone levels and allows most people to live a normal life.

Signs and Symptoms

Extreme tiredness (fatigue)
Feeling cold more than usual
Weight gain
Constipation
Difficulty concentrating or thinking clearly
Low mood or depression
Dry skin, dry hair, or hair loss
Croaky (hoarse) voice
Irregular or heavy periods

Things That Increase the Risk

Autoimmune conditions (e.g., Hashimoto's disease)
Family history of thyroid conditions
Previous thyroid surgery or radiotherapy
Treatment for an overactive thyroid
Certain medications
Iodine deficiency (rare in some areas)
Being female, especially between ages 30-50

Diagnosis

Discussion of symptoms and family medical history
Physical examination, including the neck
Blood tests to check TSH and T4 hormone levels
Referral to a specialist for further evaluation if needed

Treatment & Management

Daily hormone replacement medication (levothyroxine tablets)
Lifelong medication to prevent symptom return
Regular blood tests to adjust medication dose
Consulting a doctor or pharmacist for any side effects
Close monitoring and dose adjustment during pregnancy

Prevention

Early diagnosis and consistent treatment
Regular monitoring if you have risk factors
Promptly discussing symptoms with a doctor
Careful management of medication dosage
Close medical supervision during pregnancy

Available Treatments

Explore our range of treatment options for Underactive thyroid (hypothyroidism):