A prospective study by KK Women’s and Children’s Hospital (KKH) has found Letrozole, an aromatase inhibitor, to be safe and effective for the treatment of men with low sperm count of unknown cause.

Letrozole has been reported as a treatment option for male infertility since 2011.

“Most studies with Letrozole for male infertility have focused on men with low serum testosterone levels and testosterone-oestradiol (T/E) ratios less than 10. However, the frequency of this ratio is not as prevalent in our clinical practice,” shares primary investigator Dr Liu Shuling, Consultant, Department of Reproductive Medicine, KKH.

For the KKH study, researchers recruited men with low sperm count of unknown cause regardless of their T/E ratios. Of these, 15 of the men had a normal T/E ratio. After four months of treatment with Letrozole, 11 out of 15 men experienced improvement in either their sperm concentration or motility. Sperm concentration increased 5.5-fold and total count increased 4.3-fold.

“In the KKH study, 85 per cent of participants had a normal T/E ratio. It is heartening to note that of these, 73 per cent experienced improvement in sperm concentration, motility or count after treatment with Letrozole. This group would not have been eligible to be offered treatment under previous criteria of T/E ratios less than 10,” says Dr Liu.

A Closer Look at Semen-Analysis Parameters for Male Infertility

Low sperm count of unknown cause, or idiopathic severe oligozoospermia (sperm concentration <5 million/ml), is a common cause of male infertility. Letrozole is used in this study as treatment of male infertility to increase testosterone, decrease oestradiol and stimulate sperm production.

“As consensus on the treatment for idiopathic severe oligozoospermia is currently lacking, we wanted to take a closer look at the semen-analysis parameters for male idiopathic infertility, and measure the safety and effectiveness of Letrozole in this group of men who also have normal testosterone-oestradiol ratios.

“Our findings showed that sperm concentration and testosterone-oestradiol ratio do improve in this group of men who would otherwise not be given aromatase inhibitor treatment. Hence, Letrozole can safely be considered as a treatment option for them, as part of reproductive health management.”

Read the abstract here.