Family 9: Neuroendocrine and Hormonal Regulation
Family overview. Neuroendocrine systems — HPA axis, HPT axis, gonadal axis, GH/IGF-1 axis, and RAAS — provide the hormonal framework for metabolic, immune, and stress regulation. Their dysregulation can be primary (gland failure), secondary (central regulation failure), or tertiary (tissue-level receptor/conversion dysfunction).
Concrete mechanisms and ME/CFS evidence:
HPA axis blunting. Reduced cortisol awakening response; blunted cortisol output to stress; normal to low basal cortisol; abnormal hypothalamic-pituitary regulation rather than adrenal failure. Glucocorticoid receptor sensitivity is epigenetically reduced (Roberts et al. 2017).
Low T3 syndrome and impaired thyroid hormone conversion. Higher prevalence of low T3 syndrome in ME/CFS (16% vs 7% controls); elevated reverse T3 (rT3); normal TSH and T4 but impaired T4→T3 peripheral conversion, attributed to immune-mediated suppression of deiodinase activity. Tissue-level hypothyroidism without gland pathology (Ruiz-Núñez et al. 2018).
Sex hormone dysregulation. Altered steroid hormone profiles correlated with disease severity; dysregulation of adrenal P450c11β enzyme; menstrual cycle fluctuations worsen symptoms; perimenopause onset associated with ME/CFS exacerbation; female sex is a primary risk factor (Theoharides et al. 2024).
GH/IGF-1 axis attenuation. Attenuated basal IGF-I and IGF-II; blunted GH response to hypoglycaemia (41.9 vs 106.0 mU/L in controls), suggesting hypothalamic dysfunction or impaired GH secretion (Shalet 1998).
ADH/vasopressin downregulation. Both the renin-aldosterone and ADH systems are down-regulated despite hypovolemia; desmopressin improved symptoms in approximately half of treated patients.
Neuroendocrine-immune crosstalk. HPA blunting impairs glucocorticoid-mediated immune suppression → chronic immune activation; catecholamines suppress T cell function via β2-AR → immunosuppression and exhaustion.
Full discussion: Endocrine and Metabolic Dysfunction.
Evidence status: Probable (HPA blunting and thyroid conversion well-documented; sex hormone and GH findings preliminary but internally consistent).