Thyroid Hormones

Overview

Thyroid hormones, including thyroxine (T4) and triiodothyronine (T3), are vital for regulating metabolism, growth, and development. Produced by the thyroid gland, T4 is the primary hormone, while T3 is more active. These hormones influence nearly every organ system in the body, affecting heart rate, body temperature, weight, energy levels, and mood. The production and release of thyroid hormones are regulated by the hypothalamus and pituitary gland through a feedback loop. Imbalances in thyroid hormone levels can lead to hypo or hyperthyroidism, causing various symptoms such as fatigue, weight changes, mood disturbances, and changes in skin and hair.

General

• • two forms (T₃ and T₄)
    • T₃ is more potent than T₄
    • rT₃ is inactive
  • contain iodine
  • transported in blood bound to thyroxine-binding globulin (TBG) 

Function

• bone growth
• CNS maturation
  • recall cretinism involves short stature and mental retardation 
• increase the basal metabolic rate
  • via ↑ Na⁺/K⁺-ATPase activity
  • results in ↑ O2 consumption, RR, and body temperature
• ↑ β₁ receptors in heart
  • results in ↑ CO, HR, SV, and contractility
    • recall the importance of treating hyperthyroidism with β-blockers
• ↑ glycogenolysis, gluconeogenesis, and lipolysis

Synthesis 

• • created in the thyroid gland
  • stored in thyroid follicles
  • thyroid peroxidase responsible for oxidation, organification, and coupling 
    • forms I₂ via oxidation of I-
    • forms thyroglobulin via organification of I₂
  • T₄ converted to T₃ in peripheral tissues by outer ring deiodinase
  • T₄ converted to rT₃ by inner ring deiodinase

Regulation

• • TRH released from the hypothalamus to stimulates TSH release from the pituitary
    • TSH stimulates follicular cells to produce T₃ and T₄

Thyroid Hormones: Presentation

Introduction:

• Explain the importance of thyroid hormones in regulating body functions.
• Mention the two primary hormones: thyroxine (T4) and triiodothyronine (T3).

Thyroid Gland:

• Provide an overview of the thyroid gland’s location and structure.
• Explain how it produces and releases thyroid hormones.

Functions of Thyroid Hormones:

• Discuss the role of thyroid hormones in regulating metabolism, energy production, and body temperature.
• Highlight their influence on growth, development, and maturation.

Regulation:

• Explain the feedback loop involving the hypothalamus, pituitary gland, and thyroid gland in hormone production.
• Describe the role of thyroid-stimulating hormone (TSH) in regulating thyroid hormone release.

Imbalances and Disorders:

• Discuss hypo and hyperthyroidism, including their symptoms, causes, and effects on the body.
• Mention other thyroid-related disorders like goiter and thyroid nodules.

Diagnosis and Treatment:

• Explain common diagnostic tests, such as TSH, T4, and T3 blood tests.
• Discuss treatment options, including medication (such as synthetic thyroid hormones), radioactive iodine therapy, and surgery.

Conclusion:

• Recap the importance of thyroid hormones and their impact on overall health.
• Encourage further medical consultation for diagnosis and management of thyroid-related conditions.

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