title: Lower early morning plasma cortisol levels are associated with thyroid autoimmunity in the elderly.
abstract: OBJECTIVE
  Thyroid autoimmunity decreases in the very old. We investigated whether glucocorticoid (GC) activity, which increases in old age, is involved in this process.
  
  
  METHODS
  A total of 321 ambulatory subjects (age 51-95 years, median 71, 207 female) were studied. Thyroid function tests, cortisol, glucose, insulin and biochemical parameters were measured. A modified overnight dexamethasone suppression test (0.25 mg) was performed as an index of GC sensitivity.
  
  
  RESULTS
  Forty subjects had positive anti-thyroid peroxidase antibodies and 36 had positive anti-thyroglobulin antibodies, while 57 had either one or the other or both thyroid autoantibodies (ThAbs) positive. Mean basal cortisol levels were significantly lower in the ThAbs (+) groups (320+/-125 vs 378+/-128 nmol/l, P=0.002). Triiodothyronine, free thyroxine, post-dexamethasone cortisol levels, C-reactive protein, homeostasis model assessment-insulin-resistance-index and body mass index did not differ between these two groups. Mean age of ThAbs (+) subjects was lower compared to the ThAbs (-) group (67.38+/-7.38 vs 71.64+/-8.57 years, P=0.001).
  
  
  CONCLUSIONS
  Reduced GC activity is associated with an increased prevalence of ThAbs positivity in older ambulatory subjects. Subjects without ThAbs in this population sample are relatively older. It is not known whether this is related to increasing GC activity with age.
authors.affiliation: Endocrine Unit, Department of Medical Therapeutics, Alexandra Hospital, Athens University School of Medicine, 11528 Athens, Greece.
authors.forename: K
authors.initials: K
authors.lastname: Terzidis
authors.forename: A
authors.initials: A
authors.lastname: Panoutsopoulos
authors.forename: A
authors.initials: A
authors.lastname: Mantzou
authors.forename: P
authors.initials: P
authors.lastname: Tourli
authors.forename: G
authors.initials: G
authors.lastname: Papageorgiou
authors.forename: K
authors.initials: K
authors.lastname: Saltiki
authors.forename: C
authors.initials: C
authors.lastname: Mara
authors.forename: M
authors.initials: M
authors.lastname: Alevizaki
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000276:immunology*; D001323:Autoantibodies / Q000097:blood; D002940:Circadian Rhythm / Q000276:immunology*; D003907:Dexamethasone; D005260:Female; D005938:Glucocorticoids; D006801:Humans; D006854:Hydrocortisone / Q000097:blood*; D007453:Iodide Peroxidase / Q000276:immunology; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D013960:Thyroid Function Tests; D013967:Thyroiditis, Autoimmune / Q000175:diagnosis / Q000453:epidemiology / Q000503:physiopathology*
chemical_list: D001323:Autoantibodies; D005938:Glucocorticoids; D003907:Dexamethasone; D007453:Iodide Peroxidase; D006854:Hydrocortisone