MedDroidHypothyroidism vs Hyperthyroidism
Hypothyroidism vs hyperthyroidism: differences in symptoms, tests and treatment
Written & medically reviewed by Dr. Sanjay Anbu, MBBS · Last reviewed
Medically reviewedHypothyroidism means the thyroid makes too little hormone, so the body slows down: tiredness, weight gain, feeling cold and constipation. Hyperthyroidism means it makes too much, so the body speeds up: weight loss, a fast heartbeat, heat intolerance and anxiety. A simple TSH blood test is the first step to tell them apart.
Side-by-side comparison
| Feature | Hypothyroidism | Hyperthyroidism |
|---|---|---|
| Cause | Underactive thyroid; most often autoimmune (Hashimoto's), also iodine deficiency, after thyroid surgery or treatment | Overactive thyroid; most often Graves' disease, also toxic nodules or thyroid inflammation |
| Typical symptoms | Tiredness, weight gain, feeling cold, constipation, dry skin, hair fall, heavy periods, low mood, slowness | Weight loss despite good appetite, fast or irregular heartbeat, feeling hot, sweating, tremor, anxiety, loose stools, bulging eyes in Graves' |
| Onset & timing | Usually gradual over months or years | Can be gradual or fairly quick |
| Key tests | TSH high; free T4 low (or normal in mild cases); thyroid antibodies | TSH low; free T4 and/or T3 high; antibodies, thyroid scan if needed |
| Treatment approach | Daily thyroid hormone tablet, dose adjusted by a doctor using TSH | Antithyroid medicines, radioactive iodine or surgery; medicines to slow the heart in the short term |
| Danger signs | Rare but serious: extreme drowsiness, low body temperature, confusion (myxoedema) | Rare but serious: very high fever, very fast heartbeat, confusion, vomiting (thyroid storm) |
General patterns only. Symptoms overlap and vary from person to person. On a phone, scroll the table sideways to see both columns.
How doctors tell them apart
- TSH moves in the opposite direction to thyroid hormone: high TSH = underactive, low TSH = overactive.
- Free T4 and T3 confirm how severe it is.
- Antibody tests identify autoimmune causes.
- A thyroid scan or ultrasound may be used when there is a lump or the cause of overactivity is unclear.
See a doctor urgently if
- Very fast or irregular heartbeat, chest pain or breathlessness
- High fever with confusion or agitation
- Extreme drowsiness, confusion or very low body temperature
- Rapidly growing neck lump or difficulty breathing or swallowing
- Eye pain, double vision or worsening eye bulging
In an emergency, call your local emergency number (in India: 108 or 112).
Frequently asked questions
Can thyroid problems affect pregnancy?
Yes. Both under- and overactive thyroid need careful control before and during pregnancy. Tell your doctor if you are planning pregnancy.
Is thyroid disease lifelong?
Hypothyroidism usually needs lifelong treatment. Some forms of hyperthyroidism settle with treatment; others need a definitive treatment.
Can one turn into the other?
Sometimes. Treatment for hyperthyroidism can lead to hypothyroidism, and thyroid inflammation can cause a brief overactive phase followed by an underactive one.
Should I stop my thyroid tablet when I feel better?
No. Do not stop or change thyroid medicines without your doctor; regular TSH checks guide the dose.
Related pages
Conditions
Symptoms
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Not a diagnosis. This page gives general health information to help you talk to a doctor; it is not medical advice and does not replace an examination or tests. Do not start, stop or change any medicine without a qualified clinician. MedDroid is an AI medical assistant and can make mistakes. In an emergency, call your local emergency number (in India: 108 or 112).