TSH thyroid-stimulating hormone

Role of TSH (Thyroid-Stimulating Hormone) in the Body

TSH is a pituitary hormone that regulates the thyroid gland via a feedback mechanism.

Main Functions:

1. Stimulation of the thyroid gland – TSH prompts the thyroid to produce T4 and T3.
2. Maintaining hormonal balance – TSH rises when T3/T4 are low and falls when they are high.
3. Controlling metabolism – indirectly affects energy, weight, and body temperature.

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Symptoms of TSH Deficiency (Secondary Hypothyroidism)

Causes:

• Damage to the pituitary gland or hypothalamus (tumor, trauma, inflammation).
• Overdose of thyroid hormones (artificial TSH suppression).

Symptoms:

• Fatigue, drowsiness.
• Cold intolerance, dry skin.
• Slow heart rate, constipation.
• Difference from primary hypothyroidism: No goiter; often combined with deficiencies of other pituitary hormones.

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Symptoms of Excess TSH (Primary Hypothyroidism)

Causes:

• Autoimmune thyroiditis (Hashimoto’s disease).
• Iodine deficiency.
• Consequences of thyroid surgery.

Symptoms:

• Weight gain, swelling.
• Depression, memory impairment.
• Brittle hair/nails.
• Goiter (enlarged thyroid gland).

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Normal TSH Levels in Blood Tests

Important:

• TSH is highest at 2–4 AM and lowest in the evening.
• For borderline values, check free T4 and anti-TPO antibodies.

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What to Do if Levels Are Abnormal

If TSH is Elevated:

1. Check free T4 (to confirm hypothyroidism).
2. Test for anti-TPO antibodies (to diagnose Hashimoto’s disease).
3. Start L-thyroxine therapy (dose determined by a doctor).

If TSH is Low:

1. Rule out hyperthyroidism (T3, T4, thyroid ultrasound).
2. If pituitary insufficiency is suspected – perform brain MRI.

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Conclusion

TSH is the main «regulator» of the thyroid gland. Its deviations indicate:

• ↑ TSH – underactive thyroid (hypothyroidism).
• ↓ TSH – overactive thyroid or pituitary issues.
  Normal range: 0.4–4.0 mIU/L, but interpretation should always include T4 levels.