Metabolism
Thyroid gland
Thyroxine (T4) & T3
The thyroid hormones that set the body's overall metabolic rate.
What it does
- Control how fast the body uses energy
- Affect heart rate, temperature, weight and mood
- Essential for growth and brain development
Too much
- Overactive thyroid (hyperthyroidism): weight loss, fast heartbeat, anxiety, heat intolerance, tremor
Too little
- Underactive thyroid (hypothyroidism): tiredness, weight gain, feeling cold, dry skin, low mood
Keeping it balanced: Enough iodine and selenium support the thyroid; get symptoms checked with a blood test.
Sources & references
Think a hormone may be out of balance?
The symptoms of hormonal excess and deficiency are non-specific — tiredness, weight change, low mood and poor sleep have many everyday causes. No hormone problem can be self-diagnosed from a symptom list.
Diagnosis needs blood tests interpreted alongside your history, sometimes repeated at set times of day because many hormones vary hour to hour. Speak to a GP if symptoms are persistent; seek urgent care for severe symptoms such as confusion, fainting, chest pain or extreme thirst with frequent urination.
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