Thyroid Stimulating Hormone (TSH)

A high TSH usually indicates an underactive thyroid (primary hypothyroidism), meaning low thyroid hormone levels. Symptoms can include fatigue, weight gain, cold intolerance, constipation, dry skin, hair loss, slow heart rate, and menstrual changes; it can raise cholesterol and, if severe and untreated, risk myxedema coma. Diagnosis relies on thyroid function tests; treatment typically involves levothyroxine replacement and regular monitoring.

A normal TSH level in adults is generally about 0.4–4.0 mIU/L (some labs use 0.5–4.5 mIU/L). Values below this range suggest overactive thyroid (hyperthyroidism); values above suggest underactive thyroid (hypothyroidism). Reference ranges can vary by laboratory, age and pregnancy, so interpretation should use the lab’s stated range and clinical context; consult your clinician for personal assessment.

Typical TSH reference range is about 0.4–4.0 mIU/L. Levels above ~4 mIU/L are elevated; mild elevation (4–10) may indicate subclinical hypothyroidism and warrants monitoring, while >10 mIU/L is generally concerning for overt hypothyroidism and often needs treatment. Levels below ~0.1 mIU/L suggest clinically significant hyperthyroidism; 0.1–0.4 may indicate subclinical hyperthyroidism. Interpret with symptoms and repeat testing.

If you have a high TSH, primary treatment is appropriate levothyroxine replacement to normalize thyroid hormones; take it daily on an empty stomach, consistently, and avoid interacting supplements or drugs. Check and correct iodine and selenium status, review medications that affect thyroid function, manage stress and weight, and have regular TSH monitoring with an endocrinologist. Don’t change treatment without medical advice.

Stress by itself does not typically raise TSH. Acute stress and elevated cortisol more often suppress TSH and alter thyroid hormone conversion, causing temporary changes. However, chronic stress can dysregulate immunity and may trigger or worsen autoimmune thyroiditis in susceptible people, which can ultimately lead to elevated TSH. If you have symptoms, get thyroid function tests and discuss results with your clinician.

High TSH, indicating an underactive thyroid, can cause modest weight gain because a slower metabolism leads to increased fat storage and fluid retention. Gains are typically small to moderate and often partially reverse with appropriate thyroid hormone replacement. Other factors (diet, activity, medications) also affect weight, so abnormal TSH should be evaluated alongside symptoms and repeat testing by a clinician.