• Infertility is defined as the inability of a sexually active couple to conceive after 1 year of regular intercourse without contraception, affects approximately 15% of couples, and male factors are the cause in 20% -50% of cases.
• Infertility of unknown origin is classified into idiopathic male infertility and unexplained male infertility according to semen quality.

-Idiopathic male infertility is known as idiopathic oligoasthenoteratozoospermia, which indicates that the men have an unexplained reduction of semen quality.

In contrast, unexplained male infertility is defined as infertility of unknown origin with normal sperm parameters.

Furthermore, optimal strategies for treating idiopathic male infertility have also remained unclear.

• Data from studies in humans suggest that vitamin D receptors are present in testis, epididymis, prostate and seminal vesicles. The level of expression varies, being higher in epididymis and seminal vesicles.
• Vitamin D receptors expression was also evident in Leydig cells, as well as in normal and abnormal sperm, with the acrosomal region and the neck being the sites with the most abundant messenger ribonucleic acid expression.
• The 1,25(OH)2 D3 molecule increases intracellular calcium concentrations, sperm motility and acrosin activity, and reduces triglyceride content in sperm, actions that significantly contribute to fertilising capacity within the female reproductive tract.

Inclusion Criteria:

• infertile male patients without any detectable cause with normal clinical examination and abnormal semen parameters.

Exclusion Criteria:

• Cases with known etiology or apparent physical finding ,leukocytospermia, diminished testicular volume ,varicocele or an abnormal hormonal profile.
• couples with combined male and female factor will be excluded.

total of 30 male patients with idiopathic male infertility and other 30 fertile male (as control) will be randomly recruited from the outpatient andrology clinic of the department at Assiut university hospital.