phenotype affects entity Leydig cell differentiation abnormal Leydig cell morphology abnormal testis development abnormal cell differentiation abnormal Leydig cell differentiation abnormal LC differentiation MP:0013602 atypical formation of or inability to produce the interstitial cells that are found adjacent to the seminiferous tubules in the testicle and produce testosterone in the presence of luteinizing hormone; in most mammals, normal Leydig cell (LC) development comprises two sequential but overlapping cell lineages known as the fetal and adult type LC populations, which display distinct functional characteristics reflected by different morphology, hormonal regulation, and steroidogenic output