title: Age modifies the pituitary TSH response to thyroid failure.
abstract: OBJECTIVE
  To investigate the association between serum TSH, total T4 and various patient characteristics when hypothyroidism is diagnosed in a population, and to study how age, sex and serum T4 levels influenced pituitary TSH response.
  
  
  METHODS
  A computer-based register linked to laboratory databases prospectively identified all patients with new, biochemically overt hypothyroidism (n = 685) in an open cohort in Denmark. The diagnosis was verified in each patient, and disease was classified into nosological type. Serum TSH and total T4 were recorded at the time of diagnosis in untreated patients with spontaneous autoimmune hypothyroidism (n = 578).
  
  
  RESULTS
  In untreated primary, spontaneous autoimmune hypothyroidism, we observed a four fold difference in average serum TSH levels between the youngest (0-20 years: TSH = 100 mU/l) and the oldest (80+ years: TSH = 24.4 mU/l) group of patients. No age dependent variation was observed in serum total T4. Log TSH showed an inverse linear correlation with age. An inverse linear correlation was present between log TSH and total T4 in both young and old patients, but for all total T4 values we observed lower median serum TSH values in elderly patients.
  
  
  CONCLUSIONS
  For the same degree of thyroid failure, the serum TSH is lower among the elderly. This is most likely caused by a decrease in the hypothalamic/pituitary response to low serum T4. A certain increase in serum TSH may indicate more severe hypothyroidism in an old than in a young patient, and longer time may be needed after thyroid hormone withdrawal before elderly patients with thyroid cancer reach sufficiently high TSH values to allow for an effective radio-iodine treatment.
authors.affiliation: Department of Endocrinology and Medicine, Aalborg Hospital, Aarhus University Hospital, Denmark.
authors.forename: Allan
authors.initials: A
authors.lastname: Carlé
authors.forename: Peter
authors.initials: P
authors.lastname: Laurberg
authors.forename: Inge B
authors.initials: IB
authors.lastname: Pedersen
authors.forename: Hans
authors.initials: H
authors.lastname: Perrild
authors.forename: Lars
authors.initials: L
authors.lastname: Ovesen
authors.forename: Lone B
authors.initials: LB
authors.lastname: Rasmussen
authors.forename: Torben
authors.initials: T
authors.lastname: Jorgensen
authors.forename: Nils
authors.initials: N
authors.lastname: Knudsen
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D007037:Hypothyroidism / Q000097:blood*; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D008875:Middle Aged; D013972:Thyrotropin / Q000097:blood*; D013974:Thyroxine / Q000097:blood*
chemical_list: D013972:Thyrotropin; D013974:Thyroxine