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HUMAN · ENDOCRINOLOGY

HORMONES

ACT 01 · THE GLANDS

a handful of small organs, one bloodstream

A hormone is a message sent through the blood: made in one place, read wherever there is a receptor that fits it. The senders are small. The pituitary is the size of a pea, about half a gram. The hypothalamus above it weighs about four grams and runs much of the rest. The glands here are lit where a real scan puts them, and each glows with what it is sending at the hour on the clock. Run the day, or drag the clock.

FACT glands from an anatomical scan; curves from published studies

sources

Education only, not medical advice. Education only, not medical advice. The curves are typical healthy averages smoothed into one line. Your own levels can differ widely and still be normal, and a single blood test depends on the time, the lab and the method. Questions about your hormones belong with a doctor.

The glands are lit where an anatomical scan puts them. How brightly each one glows follows the curve of its hormone. For the hypothalamus and pituitary, which drive other glands, the glow is a drawn summary of the axes they run, not a measurement. In the last act the tissue and cells are drawn to scale, and the receptor and hormone are measured structures. The path the hormone takes into its pocket is drawn.

  1. Pruessner JC et al. Free cortisol levels after awakening: a reliable biological marker for the assessment of adrenocortical activity. Life Sci 1997;61:2539–2549.
  2. Stalder T et al. Assessment of the cortisol awakening response: expert consensus guidelines. Psychoneuroendocrinology 2016;63:414–432 (rise of roughly 38–75%, peaking 30–45 min after waking).
  3. Weitzman ED et al. Twenty-four hour pattern of the episodic secretion of cortisol in normal subjects. J Clin Endocrinol Metab 1971;33:14–22 (nadir around midnight, rise in the second half of the night).
  4. Dickerson SS, Kemeny ME. Acute stressors and cortisol responses: a theoretical integration and synthesis of laboratory research. Psychol Bull 2004;130:355–391 (cortisol peaks 21–40 min after stressor onset).
  5. Dimsdale JE, Moss J. Plasma catecholamines in stress and exercise. JAMA 1980;243:340–342 (public speaking roughly doubled plasma adrenaline).
  6. Cryer PE. Physiology and pathophysiology of the human sympathoadrenal neuroendocrine system. N Engl J Med 1980;303:436–444 (plasma catecholamine half-life of minutes).
  7. Brzezinski A. Melatonin in humans. N Engl J Med 1997;336:186–195 (night peak 02:00–04:00, low by day).
  8. Gooley JJ et al. Exposure to room light before bedtime suppresses melatonin onset and shortens melatonin duration in humans. J Clin Endocrinol Metab 2011;96:E463–E472 (duration shortened by about 90 min).
  9. Takahashi Y, Kipnis DM, Daughaday WH. Growth hormone secretion during sleep. J Clin Invest 1968;47:2079–2090.
  10. Van Cauter E, Plat L. Physiology of growth hormone secretion during sleep. J Pediatr 1996;128:S32–S37.
  11. Van Cauter E, Leproult R, Plat L. Age-related changes in slow wave sleep and REM sleep and relationship with growth hormone and cortisol levels in healthy men. JAMA 2000;284:861–868 (from 16–25 to 36–50 years, deep sleep fell from 18.9% to 3.4% of the night and GH secretion by nearly 75%).
  12. Polonsky KS, Given BD, Van Cauter E. Twenty-four-hour profiles and pulsatile patterns of insulin secretion in normal and obese subjects. J Clin Invest 1988;81:442–448 (about half of daily insulin secretion is basal).
  13. Ionescu-Tirgoviste C et al. A 3D map of the islet routes throughout the healthy human pancreas. Sci Rep 2015;5:14634 (about 3.2 million islets; other estimates are nearer one million).
  14. Brambilla DJ et al. The effect of diurnal variation on clinical measurement of serum testosterone and other sex hormone levels in men. J Clin Endocrinol Metab 2009;94:907–913.
  15. Bremner WJ, Vitiello MV, Prinz PN. Loss of circadian rhythmicity in blood testosterone levels with aging in normal men. J Clin Endocrinol Metab 1983;56:1278–1281.
  16. Bhasin S et al. Testosterone therapy in men with hypogonadism: an Endocrine Society clinical practice guideline. J Clin Endocrinol Metab 2018;103:1715–1744 (measure in the morning).
  17. Brabant G et al. Physiological regulation of circadian and pulsatile thyrotropin secretion in normal man and woman. J Clin Endocrinol Metab 1990;70:403–409.
  18. Stricker R et al. Establishment of detailed reference values for luteinizing hormone, follicle stimulating hormone, estradiol, and progesterone during different phases of the menstrual cycle. Clin Chem Lab Med 2006;44:883–887.
  19. Standring S (ed). Gray's Anatomy, 41st ed. Elsevier, 2016: gland sizes and positions.
  20. Structures (RCSB PDB, CC0): 4P6X cortisol–glucocorticoid receptor (He et al., Cell Res 2014); 4LDO adrenaline–β2-adrenergic receptor (Ring et al., Nature 2013); 4OGA insulin–insulin receptor site 1 (Menting et al., PNAS 2014); 3HHR growth hormone–receptor (de Vos, Ultsch & Kossiakoff, Science 1992); 2AM9 testosterone–androgen receptor (Pereira de Jésus-Tran et al., Protein Sci 2006); 1ERE oestradiol–oestrogen receptor α (Brzozowski et al., Nature 1997); 3GWS T3–thyroid receptor β (Nascimento et al., J Mol Biol 2006).
  21. Anatomy: BodyParts3D 4.0, © The Database Center for Life Science (DBCLS), CC BY-SA 2.1 JP. The skin, organs (with the brain) and arteries are the site's existing meshes; the hypothalamus, pineal, pituitary, adrenals, pancreas and testes are taken from the is_a set by scripts/extract-glands.mjs and re-shared under the same licence. The thyroid and ovaries are drawn, because the scan has neither.

EDUCATION ONLY · NOT MEDICAL ADVICE