Your TSH level is the most important screening marker for thyroid function. TSH (thyroid-stimulating hormone) is produced by the pituitary gland and regulates your thyroid's production of T3 and T4, which control your metabolism, energy and body temperature.
How TSH works
TSH works like a thermostat: high TSH means your thyroid is underactive (hypothyroidism), low TSH means it is overactive (hyperthyroidism). It is an inverse indicator.
Normal values
0.4-4.0 mU/L is the standard adult range. 0.4-2.5 mU/L is considered optimal. Above 4.0: potentially hypothyroid. Below 0.4: potentially hyperthyroid.
TSH too high (hypothyroidism)
Symptoms include fatigue, weight gain, feeling cold, dry skin, hair loss, low mood and concentration problems. Mild elevation (4-10 mU/L) without symptoms is called subclinical hypothyroidism.
TSH too low (hyperthyroidism)
Symptoms include restlessness, unexplained weight loss, palpitations, excessive sweating, trembling hands and sleep problems. Always requires further investigation.
Tips for reliable measurement
Have blood drawn in the morning (before 10:00), avoid biotin supplements 48 hours before, and if on thyroid medication, take it after the blood draw.
Frequently asked questions
How often should I check TSH?
With normal values, every 1-2 years is sufficient. With a known thyroid condition, every 6-12 months.
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