Basal, pulsatile, entropic (patterned), and spiky (staccato-like) properties of ACTH secretion: impact of age, gender, and body mass index.
BACKGROUND
Age, gender, and BMI determine ultradian modes of LH and GH secretion, viz., pulsatile, basal, pattern-defined regularity [approximate entropy (ApEn)] and spikiness (sharp, brief excursions). Whether the same determinants apply to ACTH secretion is not known.


METHODS
The study was conducted at a tertiary medical center.


METHODS
We studied normal women (n = 22) and men (n = 26) [ages, 23-77 yr; body mass index (BMI), 21-32 kg/m(2)].


METHODS
Volunteers underwent 10-min blood sampling to create 24-h ACTH concentration profiles.


RESULTS
Dynamic measures of ACTH secretion were studied.


RESULTS
Mean ACTH concentrations (R(2) = 0.15; P = 0.006) and both pulsatile (R(2) = 0.12; P = 0.018) and basal (nonpulsatile) (R(2) = 0.16; P = 0.005) ACTH secretion correlated directly with BMI (n = 48). Men had greater basal (P = 0.047), pulsatile (P = 0.031), and total (P = 0.010) 24-h ACTH secretion than women, including when total secretion was normalized for BMI (P = 0.019). In men, both ACTH-cortisol feedforward and cortisol-ACTH feedback asynchrony (cross-ApEn) increased with age (R(2) = 0.20 and 0.22; P = 0.021 and 0.018). ACTH spikiness rose with age (P = 0.046), principally in women. Irregularity of cortisol secretion (ApEn) increased with age (n = 48; P = 0.010), especially in men. In both sexes, percentage pulsatile ACTH secretion predicted 24-h mean cortisol concentrations (R(2) = 0.14; P = 0.009).


CONCLUSIONS
Valid comparisons of ultradian ACTH dynamics will require cohorts matched for age, gender, and BMI, conditions hitherto not satisfied in most physiological studies of this axis.
Veldhuis
Johannes D
JD
Endocrine Research Unit, Mayo Medical School, Mayo School of Graduate Medical Education, Center for Translational Science Activities, Mayo Clinic, Rochester, Minnesota 55905, USA. veldhuis.johannes@mayo.edu
Roelfsema
Ferdinand
F
Iranmanesh
Ali
A
Carroll
Bernard J
BJ
Keenan
Daniel M
DM
Pincus
Steven M
SM
D000324:Adrenocorticotropic Hormone / Q000097:blood* / Q000378:metabolism; D000328:Adult; D000368:Aged; D000375:Aging / Q000097:blood*; D015992:Body Mass Index; D002940:Circadian Rhythm; D005260:Female; D019382:Human Growth Hormone / Q000097:blood; D006801:Humans; D016014:Linear Models; D007986:Luteinizing Hormone / Q000097:blood; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D012016:Reference Values; D012727:Sex Characteristics; D055815:Young Adult
D019382:Human Growth Hormone; D000324:Adrenocorticotropic Hormone; D007986:Luteinizing Hormone