['The leucine-75-proline variant of apolipoprotein A-I leads to a new hereditary systemic amyloidosis involving mostly the liver and kidney.', 'The objective of the study was to examine the effects of this amyloidosis on testicular structure and function.', 'This was an observational study in which patients with testicular amyloidosis were characterized.', 'The study was carried out at the Endocrinology Department of Brescia University.', 'Over a 13-yr period, 25 patients were found to be affected by leucine-75-proline apolipoprotein A-I testicular amyloidosis. Thirteen had the testicle as the first or only organ involved (group 1); in 12 testicular damage followed that of other organs (group 2).', 'There were no interventions.', 'Hormone and lipidic profiles, semen analysis, echographic volume of testicles, testicular histology, and genetic analysis were carried out.', 'Group 1 patients were younger than those of group 2. In group 1, eight had hypergonadotropic hypogonadism and five were normogonadic with high gonadotropins; in group 2 all subjects were hypogonadic. All men had low high-density lipoprotein values. Group 1 patients were macroorchid, whereas the testicular volume was at the highest limit in group 2 (group 1 vs. group 2, P < 0.05). All men in the first group and six in the second group were azoospermic; the remaining had oligoposia. Biopsies showed the germinal epithelium replaced by amyloid. Leydig cells were essentially preserved in normogonadic but not hypogonadic patients.'] Does spermatogenic and steroidogenic impairment of the testicle characterize the hereditary leucine-75-proline apolipoprotein a-I amyloidosis?