Lower sex hormone-binding globulin is more strongly associated with metabolic syndrome than lower total testosterone in older men: the Health in Men Study.
BACKGROUND
Reduced circulating testosterone and sex hormone-binding globulin (SHBG) are implicated as risk factors for metabolic syndrome. As SHBG increases with age while testosterone declines, we examined the relative contributions of SHBG and testosterone to the risk of metabolic syndrome in older men.


METHODS
We conducted a cross-sectional study of 2502 community-dwelling men aged > or = 70 years without known diabetes. Metabolic syndrome was defined using the National Cholesterol Education Program-Third Adult Treatment Panel (NCEP-ATPIII) criteria. Early morning fasting sera were assayed for total testosterone, SHBG and LH. Free testosterone was calculated using mass action equations.


RESULTS
There were 602 men with metabolic syndrome (24.1%). The risk of metabolic syndrome increased for total testosterone < 20 nmol/l, SHBG < 50 nmol/l and free testosterone < 300 pmol/l. In univariate analyses SHBG was associated with all five components of metabolic syndrome, total testosterone was associated with all except hypertension, and free testosterone was associated only with waist circumference and triglycerides. In multivariate analysis, both total testosterone and especially SHBG remained associated with metabolic syndrome, with odds ratios of 1.34 (95% confidence interval (CI): 1.18-1.52) and 1.77 (95% CI: 1.53-2.06) respectively. Men with hypogonadotrophic hypogonadism (total testosterone < 8 nmol/l, LH < or = 12 IU/l) had the highest prevalence of metabolic syndrome (53%, P<0.001).


CONCLUSIONS
Lower SHBG is more strongly associated with metabolic syndrome than lower total testosterone in community-dwelling older men. SHBG may be the primary driver of these relationships, possibly reflecting its relationship with insulin sensitivity. Further studies should examine whether measures that raise SHBG protect against the development of metabolic syndrome in older men.
Chubb
S A Paul
SA
PathWest, Department of Biochemistry, Fremantle Hospital, Western Australia, 6160 Australia.
Hyde
Zoë
Z
Almeida
Osvaldo P
OP
Flicker
Leon
L
Norman
Paul E
PE
Jamrozik
Konrad
K
Hankey
Graeme J
GJ
Yeap
Bu B
BB
D000368:Aged; D000369:Aged, 80 and over; D001315:Australia; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D024821:Metabolic Syndrome / Q000097:blood* / Q000175:diagnosis; D015999:Multivariate Analysis; D011446:Prospective Studies; D012307:Risk Factors; D012738:Sex Hormone-Binding Globulin / Q000378:metabolism*; D013739:Testosterone / Q000097:blood*
D012738:Sex Hormone-Binding Globulin; D013739:Testosterone