Influence of Administration Route of Testosterone on Male Fertility

Inclusion Criteria: * Age greater than or equal to 50 years but not older than 80 years of age; * Serum testosterone level \<13.8 nmol/l; * Sperm concentration \> 40 Million/ml; * Willing to give written informed consent. Exclusion Criteria: * Testicular diseases or having had any surgical procedures applied to the testes; * History or currently existing serious disease of any type, in particular liver, kidney or heart disease, any form of diabetes mellitus, cancer or psychiatric illness; * Current androgen, anabolic steroid or sex hormone treatment or any treatment with such compounds in the previous 6 months; * Blood donation within the 12-week period before the initial study dose. * History of, or current nasal disorders (e.g. seasonal or perennial allergic rhinitis, atrophic rhinitis, polyposis, abuse of nasal decongestants, clinically relevant nasal septum deviation, recurrent epistaxis) or sleep apnea; * Elevated serum PSA levels (\> 4 ng/ml for subjects \>= 50 years of age);