Jc. Froehlich et al., Analysis of heritability of hormonal responses to alcohol in twins: Beta-endorphin as a potential biomarker of genetic risk for alcoholism, ALC CLIN EX, 24(3), 2000, pp. 265-277
Background: Hormonal responses to alcohol have been reported to differ in s
ubjects with and without a family history of alcoholism which suggests that
alcohol-induced hormonal changes might be used to identify individuals who
are at elevated genetic risk for developing alcoholism. However, before a
biological response can be used as a marker of genetic risk for disease, it
must first be demonstrated that the response is, in fact, heritable. The p
resent study was designed to determine whether hormonal responses to alcoho
l are heritable.
Methods: The adrenocorticotropic hormone (ACTH), beta-endorphin (beta-E), c
ortisol (CORT), and prolactin (PRL) responses to alcohol were examined in m
ale and female identical (monozygotic or MZ) and fraternal (dizygotic or DZ
) twin pails. Male subjects consumed 0.35 g ethanol/kg body weight (BW) and
females consumed 0.325 g ethanol/kg BW in each of two alcohol drinking ses
sions administered 1 hr apart (total dose of 0.7 g/kg BW in males and 0.65
g/kg BW in females). Plasma hormone content was analyzed in samples collect
ed before (resting conditions) and at 15, 60, 75, 120, 180, and 240 min aft
er onset of drinking. Hormonal responses to alcohol were examined with twin
analyses using the TWINAN90 program. A separate analysis was performed for
each of the four hormones. A subset of subjects from each zygosity was see
n on two separate occasions to establish retest reliability. Heritability o
f hormonal responses to alcohol was estimated using the intraclass correlat
ion approach before and after removing the contribution of covariates that
have the potential of influencing the plasma levels of these hormones.
Results: Resting plasma levels of all four hormones were within the expecte
d range, and the beta-E ACTH, and PRL responses to the alcohol challenge ev
idenced good test-retest reliability. Of the four hormones examined, the on
ly one that showed significant heritability after alcohol drinking was beta
-E. Heritability estimates were not altered for any of the four hormones af
ter removal of the variance contributed by covariates, such as gender and a
ge.
Conclusions: Taken together with other recent findings, the results suggest
that the beta-E response to alcohol may represent a new biomarker that can
be used to identify individuals who are at elevated genetic risk for devel
oping alcoholism.