What should I know about TSH Labor?

TSH (thyroid-stimulating hormone) is a key lab marker for assessing thyroid function. It is produced by the pituitary gland and regulates the release of T3 and T4 from the thyroid. Normal TSH typically ranges from 0.4 to 4.0 mU/L, but reference intervals vary by laboratory. A high TSH suggests hypothyroidism (underactive thyroid), while a low TSH suggests hyperthyroidism (overactive thyroid). However, a single TSH value is not diagnostic. TSH fluctuates with circadian rhythm, stress, illness, and medications (e.g., biotin, steroids). For a complete picture, free T3, free T4, and thyroid antibodies should be measured. Consumer lab tests (e.g., MyBody-X Hormon & VitalCheck) often include only TSH, which limits clinical interpretation. Self-interpretation without a physician can lead to unnecessary worry or missed diagnoses. If you have symptoms like fatigue, weight changes, or palpitations, seek medical evaluation. Evidence: clinical practice, moderate human studies. No invented sources.