Increased Thyroid-Stimulating Hormone (TSH)

• Primary Hypothyroidism – Conditions such as Hashimoto’s thyroiditis (an autoimmune thyroid disorder) lead to decreased thyroid hormone production; low T₃/T₄ levels relieve negative feedback, causing an increase in TSH.
• Iodine Deficiency – Insufficient iodine intake reduces thyroid hormone synthesis, prompting a compensatory TSH rise.
• Resistance to Thyroid Hormone – Rarely, a condition where tissues are less responsive to thyroid hormones can lead to high TSH.
• Life-Stage Considerations – In neonates, screening for TSH is standard to detect congenital hypothyroidism. Older adults may have mildly elevated TSH levels due to age-related changes in thyroid function.

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Decreased Thyroid-Stimulating Hormone (TSH)

• Hyperthyroidism – Disorders such as Graves’ disease (an autoimmune hyperthyroidism) lead to excess thyroid hormone production, which suppresses TSH via negative feedback.
• Central Hypothyroidism – If the pituitary or hypothalamus is dysfunctional (due to tumors, trauma, or autoimmune hypophysitis), TSH production may be low despite low thyroid hormone levels.
• Life-Stage Considerations – In children, low TSH with high thyroid hormones may indicate neonatal or childhood hyperthyroidism, while in adults, abnormal low TSH must be interpreted in the context of clinical symptoms and free hormone measurements.

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Thyroid Function

• Common Thyroxine (T4), Free Thyroxine (FT4), Free Triiodothyronine (FT3):
  These markers measure the overall thyroid hormone production and the bioavailable (active) fractions. While Common T4 reflects total hormone levels (both bound and free), FT4 and FT3 specifically indicate the unbound, active hormones that drive metabolic processes.
  
  
• Thyrotropic Hormone (TSH):
  This pituitary hormone regulates thyroid hormone synthesis through a negative feedback mechanism. Elevated or suppressed TSH levels provide insight into thyroid function and help direct further evaluation of thyroid disorders.
  
  
• Thyroxine Binding Globulin (TBG):
  TBG is the main protein binding thyroid hormones in the blood. It influences the proportion of hormone that remains free versus bound, affecting the interpretation of Common T4 compared to FT4 and FT3 levels.
  
  
• thyreoglobulin;calcitonin; tumerous marker thyreoglobulin:
  These markers focus on thyroid tissue activity and neoplastic surveillance.
  
  
  
  • thyreoglobulin reflects the functional activity of thyroid follicular cells.
  • When used as a tumour marker (tumerous marker thyreoglobulin), it helps monitor for residual or recurrent differentiated thyroid cancer following treatment.
  • calcitonin, secreted by the thyroid’s C cells, is particularly valuable in detecting medullary thyroid carcinoma.

Together, these markers offer a comprehensive view of thyroid gland function, regulation, and tissue integrity, integrating hormonal activity with diagnostic tools for thyroid cancer surveillance.

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