These two conditions involve the same gland but produce almost opposite symptoms.
| Feature | Hypothyroidism | Hyperthyroidism |
|---|---|---|
| Thyroid activity | Underactive — too little hormone | Overactive — too much hormone |
| Weight | Weight gain | Weight loss despite normal appetite |
| Energy | Fatigue, sluggishness | Restlessness, anxiety |
| Heart rate | Slower than normal | Faster, palpitations |
| Temperature sensitivity | Cold intolerance | Heat intolerance, excess sweating |
The thyroid gland produces too little hormone, slowing down the body's metabolism — leading to fatigue, weight gain, cold sensitivity, and often dry skin or hair thinning.
The opposite — excess thyroid hormone speeds up metabolism, causing weight loss, a racing heart, anxiety, and heat intolerance, sometimes with visible eye changes in some cases.
A racing heart with chest pain, or severe fatigue with confusion, both need prompt evaluation — untreated thyroid imbalances can affect heart rhythm and other organs over time.
This comparison is for general awareness only and cannot replace a medical diagnosis. Many conditions share overlapping symptoms — a doctor can examine and test to tell them apart accurately.