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TSH

Thyroid-Stimulating Hormone Test — at Concierge Endocrinology of New Jersey

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Overview

A TSH test is a blood test that measures the amount of thyroid-stimulating hormone (TSH) in your blood. TSH is a hormone produced by the pituitary gland in your brain that tells your thyroid how much thyroid hormone to produce.

Thyroid hormones control how your body uses energy, affecting almost every organ. They control many of your body's most important functions, such as breathing, heart rate, weight, digestion, and mood. If you have too much thyroid hormone, many of your body's functions speed up. If you have too little, many functions slow down.

A TSH test can help determine if your thyroid is working correctly. It can tell you if you have hyperthyroidism (too much thyroid hormone) or hypothyroidism (too little thyroid hormone). However, a TSH test alone cannot show what is causing the thyroid problem — additional tests may be needed.

Signs & Symptoms

Symptoms of too much thyroid hormone (low TSH): weight loss, rapid or irregular heartbeat, nervousness, trouble sleeping, fatigue, shaky hands, muscle weakness, sweating, frequent bowel movements, goiter
Symptoms of too little thyroid hormone (high TSH): weight gain, sensitivity to cold, joint and muscle pain, dry skin, thinning hair, heavy or irregular periods, fertility problems, depression, constipation, fatigue

Causes & Risk Factors

The most common cause of hyperthyroidism (low TSH) is Graves' disease
The most common cause of hypothyroidism (high TSH) is Hashimoto's disease
Both Graves' disease and Hashimoto's disease are autoimmune disorders
In rare cases, an abnormal TSH result may indicate a pituitary gland problem
Thyroid nodules, thyroiditis, or thyroid surgery can also affect TSH levels
Certain medications can influence TSH readings

Diagnosis

A TSH test is the primary way to diagnose a thyroid problem. It is a simple blood test that can be done at any time, though some providers prefer morning testing.

If the TSH results are not normal, additional thyroid blood tests will likely be ordered to determine the cause. These may include a T4 thyroid hormone test (free T4), a T3 thyroid hormone test, and thyroid antibody tests (anti-TPO, anti-thyroglobulin, TSI).

TSH levels can be affected by serious illnesses, pregnancy, and age. For example, TSH levels may be higher in people over age 80 even without a thyroid problem. During the first three months of pregnancy, TSH levels are often a little low.

Treatment Options

If diagnosed with hypothyroidism (high TSH): thyroid hormone replacement medicine (levothyroxine)
If diagnosed with hyperthyroidism (low TSH): antithyroid medications, radioiodine therapy, or surgery
Regular TSH tests to monitor thyroid hormone levels and ensure correct medication dosing
Lifelong thyroid hormone medicine if the thyroid has been removed
Adjustment of medication doses based on periodic TSH monitoring
Comprehensive evaluation to determine the underlying cause of abnormal TSH

Important Facts

TSH is the most sensitive and commonly used test for evaluating thyroid function.

Normal TSH range is typically 0.4 to 4.0 mIU/L, though ranges may vary slightly by laboratory.

Newborn babies are routinely screened with a TSH test to check for congenital hypothyroidism.

TSH levels can fluctuate due to illness, pregnancy, medications, and age — context matters for interpretation.

Medical information adapted from MedlinePlus — U.S. National Library of Medicine. Always consult with your physician for personalized medical advice.

Expert TSH Care

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