Hormone secretion, transport, binding proteins and feedback control
Pulsatile and circadian secretion, the binding proteins that carry thyroid and steroid hormones and how changes in them distort total hormone levels, half-life and time to steady state, and the feedback logic that underlies paired hormone testing, dynamic tests and assay interference.
Tier 1Medical sciences concept
Written with AI assistance and fact-checked against the sources below. For exam study, not clinical decisions. How notes are made
At a glance
- Secretion follows pulses, circadian rhythms and stimuli. A single random level of GH, LH or cortisol can mislead.
- Thyroid and steroid hormones travel bound to carrier proteins. Only free hormone acts and is under feedback control, so changes in binding proteins move the total level and leave the free level alone.
- Half-life sets how fast a level responds to treatment: about 6 weeks to steady state for T4, minutes for insulin and PTH.
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Sources
- Williams Textbook of Endocrinology (15th ed.)Elsevier (Melmed, Auchus, Goldfine, Rosen, Kopp, 2024), 2024
- Guyton and Hall Textbook of Medical Physiology (14th ed.)Elsevier (Hall and Hall, 2021), 2021
- Nieman LK, Biller BMK, Findling JW, et al. The diagnosis of Cushing's syndrome: an Endocrine Society clinical practice guideline. J Clin Endocrinol Metab 2008;93(5):1526-40Endocrine Society, 2008
- Hamrahian AH, Oseni TS, Arafah BM. Measurements of serum free cortisol in critically ill patients. N Engl J Med 2004;350(16):1629-38New England Journal of Medicine, 2004
- Favresse J, Burlacu MC, Maiter D, Gruson D. Interferences with thyroid function immunoassays: clinical implications and detection algorithm. Endocr Rev 2018;39(5):830-50Endocrine Reviews, 2018
- Evans L, Rhodes A, Alhazzani W, et al. Surviving Sepsis Campaign: international guidelines for management of sepsis and septic shock 2021. Crit Care Med 2021;49(11):e1063-143Society of Critical Care Medicine and European Society of Intensive Care Medicine, 2021
- Last updated
- 14 November 2026
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