Triiodothyronine

Triiodothyronine, also known as T3, is a thyroid hormone that plays crucial roles in the body's overall metabolism, growth, and development. It is produced by the thyroid gland and is the more biologically active hormone out of the two thyroid hormones. The other hormone is thyroxine (T4), which is converted into T3 in the body's peripheral tissues.

Production and Function

Triiodothyronine is primarily produced from the deiodination of thyroxine (T4) in peripheral tissues. This process is regulated by the thyroid-stimulating hormone (TSH), which is released from the pituitary gland. T3 then enters cells and binds to nuclear receptors, influencing the transcription of various genes.

The functions of T3 include increasing the basal metabolic rate, affecting protein synthesis, helping to regulate long bone growth, and aiding in brain development. It also plays a role in maintaining body temperature, heart rate, and blood pressure.

Clinical Significance

Abnormal levels of T3 can lead to various medical conditions. High levels can result in hyperthyroidism, characterized by weight loss, increased heart rate, and anxiety. On the other hand, low levels can lead to hypothyroidism, which can cause fatigue, weight gain, and depression.

Measurement of T3 levels is part of the diagnostic process for thyroid disorders. It is also used to monitor the effectiveness of treatment for these conditions.

See Also

• Thyroid function tests
• Thyroid disease
• Thyroid hormones

References

Triiodothyronine Resources
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