The aim of this cross-sectional study was to analyze bone mineral density (BMD) 
and prevalence of osteopenia and osteoporosis in 30 men with prolactinoma, and 
compare them to 22 control subjects. BMD of lumbar spine and femur was evaluated 
by dual-energy X-ray absorptiometry. PRL, testosterone, estradiol, sexual 
hormone-binding globulin and free androgen and estrogen indexes (FAI and FEI, 
respectively) were measured in all the subjects. In patients with prolactinoma, 
mean values of PRL and testosterone were calculated for the 12-month period that 
preceded the study. The mean T-score of the four sites analyzed by bone 
densitometry was lower in men with prolactinoma than in controls (p-values: 
lumbar spine=0.015, femoral neck <0.0001, trochanter=0.037, total femur=0.036), 
and 55.6% of the former presented osteopenia or osteoporosis at one or more 
sites (p =0.035). The lumbar spine was the most seriously affected site, where 
29.6% had osteopenia and 14.8% had osteoporosis. By the time of BMD 
determination, significant associations were found between BMD and PRL, 
testosterone, FAI, estradiol, FEI, and duration of hypogonadism. Considering the 
period of 12 months that preceded BMD evaluation, trochanter BMD was associated 
with mean PRL levels, while there was an association between lumbar spine BMD 
and mean testosterone levels. However, the multiple regression analysis showed 
that estradiol was the main determinant of BMD. In conclusion, men with 
prolactinoma have high prevalence of osteopenia and osteoporosis. Bone loss in 
such patients is associated with hyperprolactinemia and hypogonadism, and mainly 
influenced by estrogen.