Thyroid-Stimulating Hormone (TSH) is a hormone produced by the pituitary gland that plays a crucial role in regulating the thyroid gland. It stimulates the thyroid to produce thyroxine (T4) and triiodothyronine (T3), which are essential for metabolism, energy production, and overall body function.

Key Functions of TSH

• Stimulates the thyroid gland to release T3 and T4.
• Helps regulate metabolism, body temperature, and energy levels.
• Works through a feedback loop with the hypothalamus and thyroid to maintain hormone balance.

Normal TSH Levels (May Vary by Lab)

• Adults: ~0.4 to 4.0 mIU/L
• Pregnant women: Lower TSH levels are common.
• Children: Slightly different reference ranges.

High TSH (Hypothyroidism)

A high TSH level may indicate an underactive thyroid (hypothyroidism), meaning the thyroid isn’t making enough hormones. Possible causes:

• Hashimoto’s thyroiditis (an autoimmune disorder)
• Iodine deficiency
• Certain medications (e.g., lithium)

Low TSH (Hyperthyroidism)

A low TSH level may suggest an overactive thyroid (hyperthyroidism), meaning too much T3 and T4 are being produced. Possible causes:

• Graves’ disease (an autoimmune disorder)
• Excessive iodine intake
• Thyroid nodules producing too much hormone

When to Test for TSH?

Doctors may recommend a TSH test if you have symptoms like:

• Fatigue or weight gain (hypothyroidism)
• Rapid heartbeat or weight loss (hyperthyroidism)
• Depression, hair thinning, or irregular periods