What is the gender distribution with regards to etiology of infertility?

A 33-year-old man is referred for evaluation of male infertility. He and his 29 years old wife have been trying to conceive for last 2 years. She is gravida (G0), para (P0) with complete medical evaluation revealing regular ovulatory cycles and normal reproductive anatomy with no history of reproductive tract disorders, pelvic infection or surgery. The couple has had unprotected vaginal intercourse at least 2–3 times a week, having undergone a normal puberty and well previously, he complains of poor libido and poor erection with decreased volume of ejaculate for past 1 year. He shaves once a week. There is no past history of any chronic ailments or any reproductive disorders, and has taken no medications or any illicit drugs. He has no family history of hypogonadism, cleft palate or infertility; he has 2 brothers who have fathered children. He works as a software professional with no habitual smoking or drinking. He has never fathered a child. He is well virilized with normal male voice and normal upper/lower segment ratio. His body mass index (BMI) is 33.5 kg/m2 with bilateral nontender gynecomastia; a normal genitourinary examination with normally descended testes that are 12 mL bilaterally and easily palpable vasa deferentia. His laboratory tests (performed at 8.00 am) reveal total testosterone 220 ng/dL (N: 300–1000 ng/dL), luteinizing hormone (LH)-2 mIU/mL, follicle stimulating hormone (FSH)-6 mIU/ mL. Hematogram, urine analysis, hepatic and renal profiles, serum prolactin, thyroid profile and iron studies are normal. Repeat hormonal analysis reveal similar results. The seminal fluid analysis yields no sperms with volume of 2.45 mL, normal pH (≥7.2) and fructose. Repeat semen analysis shows similar results. Sella imaging reveals no hypothalamic/pituitary abnormality.

What is the gender distribution with regards to etiology of infertility?