TSH – Thyroid Stimulating Hormone

The TSH (Thyroid Stimulating Hormone) test measures the level of TSH in the blood. TSH is produced by the pituitary gland and regulates the production of thyroid hormones (T3 and T4) by the thyroid gland. This test is the most commonly used screening tool to assess thyroid function and detect thyroid disorders.

1. What Is TSH?

• TSH is a hormone secreted by the pituitary gland in the brain.

• It stimulates the thyroid gland to produce and release thyroxine (T4) and triiodothyronine (T3).

• TSH levels adjust in response to circulating levels of T3 and T4 through a feedback loop.

2. Why Is the TSH Test Performed?

This test is used to:

• Screen for thyroid dysfunction (hypothyroidism or hyperthyroidism).

• Monitor thyroid replacement therapy (e.g., levothyroxine).

• Evaluate symptoms like fatigue, weight changes, depression, or irregular menstrual cycles.

• Help diagnose pituitary disorders.

3. TSH Reference Range

• Normal: 0.4 – 4.5 mIU/L (milli-international units per liter)

• Optimal range may vary depending on age, pregnancy, and lab standards.

4. Interpreting TSH Results

🔹 High TSH:

• Suggests hypothyroidism (underactive thyroid).

• Common causes: Hashimoto’s thyroiditis, iodine deficiency, or insufficient thyroid hormone treatment.

🔹 Low TSH:

• Suggests hyperthyroidism (overactive thyroid).

• Common causes: Graves’ disease, thyroid nodules, or excess thyroid hormone medication.

• May also indicate pituitary dysfunction if accompanied by low T3 and T4.

5. What Can Affect TSH Levels?

• Thyroid medications (levothyroxine, antithyroid drugs)

• Pituitary disorders or brain injury

• Severe illness, stress, or certain medications (e.g., steroids, dopamine agonists)

• Pregnancy and hormonal fluctuations

6. How Is the Test Performed?

• A blood sample is drawn from a vein, typically in the morning.

• No fasting is required unless ordered with other tests.

7. When to See a Doctor

🚨 Speak with your healthcare provider if you:

• Experience symptoms such as fatigue, weight gain/loss, cold or heat intolerance, or hair thinning.

• Have a family history of thyroid disease or autoimmune conditions.

• Are pregnant or planning pregnancy and need thyroid function screening.

🔹 Key Takeaways

✅ TSH is the primary marker for evaluating thyroid gland function.

✅ High levels typically indicate hypothyroidism, while low levels suggest hyperthyroidism.

✅ Regular monitoring is crucial for individuals with thyroid disorders or on hormone therapy.