C. Wang et al., Effects of transdermal testosterone gel on bone turnover markers and bone mineral density in hypogonadal men, CLIN ENDOCR, 54(6), 2001, pp. 739-750
OBJECTIVE Androgen replacement has been reported to increase bone mineral d
ensity (BMD) in hypogonadal men. We studied the effects of 6 months of trea
tment with a new transdermal testosterone (T) gel preparation on bone turno
ver markers and BMD.
DESIGN This was a prospective, randomized, multicentre, parallel clinical t
rial where 227 hypogonadal men, mean age 51 years (range: 19-68 years) were
studied in 16 academic and research institutions in the USA. Subjects were
randomized to apply 1% T gel containing 50 or 100 mg T (delivering approxi
mately 5-10 mg T/day) or two T patches (delivering 5 mg T/day) transdermall
y for 90 days. At day 91, depending on the serum T concentration, the T gel
dose was adjusted upward or downward to 75 mg T/day until day 180. No dose
adjustment occurred in the T patch group.
MEASUREMENTS Serum T, free T and oestradiol, bone turnover markers and BMD
were measured on days 0, 30, 90 and 180 before and after treatment.
RESULTS Application of T gel 100 mg/day resulted in serum T concentrations
1.4 and 1.9-fold higher than in the T gel 50 mg/day and the T patch groups,
respectively, Proportional increases occurred in serum oestradiol. Urine N
-telopeptide/creatinine ratio, a marker for bone resorption, decreased sign
ificantly (P = 0.0019) only in the T gel 100 mg/day group, Serum bone osteo
blastic activity markers (osteocalcin, procollagen and skeletal alkaline ph
osphatase) increased significantly during the first 90 days of treatment wi
thout intergroup differences but declined to baseline thereafter. BMD incre
ased significantly both in the hip (+1.1 +/- 0.3%) and spine (+2.2 +/- 0.5%
) only in the T gel 100 mg/day group (P = 0.0001).
CONCLUSIONS Transdermal testosterone gel application for 6 months decreased
bone resorption markers and increased osteoblastic activity markers for a
short period, which resulted in a small but significant increase in BMD. On
going long-term studies should answer whether the observed increases in BMD
are sustained or continue to be dependent on the dose of testosterone admi
nistered.