TSH is produced by the pituitary gland and stimulates the thyroid to release T3 and T4 hormones.

It acts as a feedback regulator:

High TSH → thyroid underactive (hypothyroidism).

Low TSH → thyroid overactive (hyperthyroidism).

Clinical uses include:

First‑line test for thyroid dysfunction.

Monitoring thyroid hormone replacement therapy.

Evaluating goiter, thyroid nodules, and autoimmune thyroid disease.

Often performed alongside T3, T4, and thyroid antibody tests for a complete thyroid profile.

Analyte: Thyroid Stimulating Hormone (TSH) in serum (mIU/L).

Normal Range (varies by lab): ~0.4–4.0 mIU/L.

Abnormal Findings:

High TSH: Hypothyroidism, Hashimoto’s thyroiditis, inadequate thyroid hormone therapy.

Low TSH: Hyperthyroidism, Graves’ disease, excessive thyroid hormone therapy, pituitary dysfunction.

Clinical Use:

Provides a direct measure of pituitary regulation of thyroid gland.

Helps guide diagnosis, treatment, and monitoring of thyroid disorders.

Supports endocrinology and internal medicine evaluations.