What is the main reproductive investigation for a male whose partner has normal fertility and they have been trying to conceive for two years?

The primary reproductive investigation for a male in the context of infertility, especially when the female partner has normal fertility and the couple has been trying to conceive for two years, is typically a semen analysis. This test assesses various important parameters of semen, including sperm concentration, motility, morphology, and semen volume. Examining these factors helps to identify potential male infertility issues.

While hormonal profiles can be useful in evaluating conditions like hypogonadism, which can affect fertility, they are not the first-line investigation in the scenario where infertility is present. A chlamydia test, while important for identifying sexually transmitted infections that may impact fertility, is not a direct measure of male reproductive capability. Sperm motility analysis is a component of the overall semen analysis rather than a standalone test.

In this case, focusing on semen volume and other parameters will provide the most comprehensive understanding of male fertility status. Thus, choosing a semen analysis as the main investigation is crucial for determining if there are underlying issues contributing to the couple's difficulties in conceiving.