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RISK FACTORS ASSOCIATED WITH THE METABOLIC SYNDROME: STUDIES IN
A GENERAL POPULATION
Svartberg, J.
Dept. of Medicine, University Hospital of North Norway, N-9038, Tromso,
Norway
The Tromsų Study is a population-based health survey primarily focusing
on cardiovascular diseases. In the fourth survey,
which took place from 1994 to 1995, all men and women
aged 25 years or older were invited and 80% (27 159)
individuals attended. All participants aged 55 to
74 years plus random 5% samples of subjects in the
other age groups were invited to a second visit for
a more extensive examination. A total of 6891 subjects
(3393 men) attended the second visit, representing
79% of the eligible population. Serum samples were
drawn for the future analyses of sex hormones in a
sub- sample of 1605 men. Thus sex hormone analyzes
were performed for 1605 men of whom 1565 men had sufficient
serum for all hormone data. Our study confirmed an
age-related decline of total testosterone, and an
even steeper decline of free testosterone was seen
due to the age-related increase in SHBG. Body mass
index and smoking were independent contributors to
the variation of total and free testosterone and SHBG
levels, and coffee consumption to the variation of
total testosterone and SHBG. Thus, life-style factors
had a direct effect on circulating levels of free
endogenous sex hormones and to total levels due to
the effect on SHBG levels. Data from the Tromsų men
also showed strong evidence of a seasonal variation
of total and free testosterone, associated with a
seasonal variation in waist-to-hip ratio. Low levels
of testosterone, hypogonadism, have several common
features with the metabolic syndrome, and in the Tromsų
men we found that testosterone levels were inversely
associated with anthropometrical measurements such
as waist circumference. The lowest levels of total
and free testosterone were found in men with the most
pronounced central obesity. It is likely that decreasing
levels of testosterone stimulates the central fat
distribution and thus could increase the risk of cardiovascular
disease and mortality. Total testosterone was inversely
associated with systolic blood pressure, and men with
hypertension had lower levels of total and free testosterone.
Inverse associations were also seen between total
testosterone with left ventricular mass, and men with
left ventricular hypertrophy had lower levels of total
testosterone. Preliminary data also suggests that
testosterone levels are inversely associated with
intima-media thickness, a measurement of subclinical
atherosclerosis. Furthermore we found that men with
diabetes had lower testosterone levels compared to
men without a history of diabetes, and an inverse
association between testosterone level and percent
glycosylated hemoglobin was found. In summary, maintaining
a testosterone level in the normal range seems beneficial
for all men.
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