Men were eligible to participate if they had two morning blood samples with age-adjusted low testosterone levels, and a total motile sperm count more than 5 million/ejaculation. Participants received 11-mg nasal testosterone gel three times daily for 6 months.
By 1 month into the study, 43 patients had a median testosterone level of 573 ng/dL. Fifteen patients have thus far completed all 6 months of the study and they had a median testosterone level of 604 ng/dL.
At baseline, sperm concentration was a mean 21.32 million/mL with 50% motility, and a total sperm count of 32.23 million/ejaculation. Sperm concentration at 6 months was unchanged at a median 21 million/mL.
Motility was preserved at a median 51.5% after 6 months of therapy, a statistically insignificant difference from 54% motility at baseline. Total motile sperm count decreased from a median 29.3 million/ejaculation at baseline to 19.5 million/ejaculation, a difference that didn’t reach statistical significance.
“What that means is that this nasal testosterone gel [could] be used in men who have low testosterone and are interested in preserving fertility,” said Dr. Masterson.
Dr. Ramasamy said that they’re seeing early confirmation of their initial hypothesis about the nasal gel formulation in this interim analysis. “Because it’s short acting, we believe some of the GnRH pulses and the LH and FSH that are released by the pituitary gland are still maintained, compared with the other forms of testosterone therapy, which can cause complete suppression of the [HPG] axis.”
In discussion with attendees at the poster session at which the research was featured, Dr. Masterson explained that quality-of-life measures were also collected as part of the study and will be presented separately. In addition to information about erectile function, men were asked about libido – a more complex phenomenon than erectile function alone – and early analysis showed a robust response, he said.
He acknowledged that it is not known whether craniofacial circulation facilitates testosterone transport to the brain when the nasal gel testosterone formulation is used, but that it is mechanistically plausible.
Dr. Masterson added that, practically speaking, patients should be aware that the formulation is a gel. “It sort of has to be painted on” the nasal septum within the nostrils, he said.
Aytu BioScience, which markets Natesto, partially supported the study. Dr Masterson reported no disclosures or conflicts of interest.