Triiodothyronine

Definition

Triiodothyronine, commonly known as T3, is a thyroid hormone that plays a crucial role in regulating metabolism, growth, and development in the body. It is one of the main hormones produced by the thyroid gland, alongside thyroxine (T4), and is essential for maintaining energy levels and overall metabolic function. T3 influences many physiological processes, including heart rate, body temperature, and the rate at which the body uses fats and carbohydrates.

5 Must Know Facts For Your Next Test

1. Triiodothyronine is produced from the conversion of thyroxine (T4) in target tissues and has a more potent effect on metabolism than T4.
2. T3 influences various metabolic processes, such as increasing the basal metabolic rate (BMR), enhancing protein synthesis, and promoting the breakdown of fats.
3. The production of T3 is regulated by the hypothalamus and pituitary gland through a feedback loop involving Thyroid Stimulating Hormone (TSH).
4. Deficiencies or excesses in T3 levels can lead to serious health issues, including weight gain, fatigue, or hyperactivity.
5. T3 is also involved in brain development and function, making it crucial for cognitive abilities during early life stages.

Review Questions

• How does triiodothyronine (T3) interact with other hormones to regulate metabolism?
  • Triiodothyronine (T3) interacts closely with other hormones like thyroxine (T4) and Thyroid Stimulating Hormone (TSH) to regulate metabolism. The hypothalamus releases Thyrotropin-releasing hormone (TRH), stimulating the pituitary gland to secrete TSH. This promotes the thyroid gland to produce T3 and T4. Once sufficient levels of these hormones are reached, they provide negative feedback to reduce TRH and TSH production, maintaining hormonal balance.
• Discuss the physiological effects of triiodothyronine on the body's metabolism.
  • Triiodothyronine (T3) has significant physiological effects on metabolism by increasing the basal metabolic rate (BMR), enhancing protein synthesis, and promoting lipolysis. It helps regulate how quickly the body uses energy from food while also affecting heart rate and body temperature. The overall result is a coordinated response that ensures energy homeostasis and supports various bodily functions.
• Evaluate the implications of abnormal triiodothyronine levels on overall health.
  • Abnormal levels of triiodothyronine (T3) can have serious health implications. Elevated levels can lead to hyperthyroidism, characterized by symptoms like increased heart rate, weight loss, and anxiety. Conversely, low levels result in hypothyroidism, causing fatigue, weight gain, and depression. Both conditions underscore the importance of maintaining optimal T3 levels for overall well-being, affecting not just metabolism but also cardiovascular health and cognitive function.

Related terms

Thyroxine: Thyroxine, or T4, is another primary hormone produced by the thyroid gland that regulates metabolism and energy levels, serving as a precursor to triiodothyronine.

Thyroid Gland: The thyroid gland is an endocrine gland located in the neck that produces hormones like T3 and T4, which are vital for regulating metabolism and growth.

Hypothyroidism: Hypothyroidism is a condition where the thyroid gland does not produce enough thyroid hormones, including T3, leading to a range of metabolic and health issues.