Pyriform head: a frequent but little-studied morphological abnormality of sperm

This study was conducted to investigate the frequency of sperm with a pyriform head in semen samples, to determine the percentage of the occurrence of this abnormal sperm form, and to assess its possible correlation with other semen parameters. The study was designed as a retrospective data analysis in the setting of an andrology laboratory at a tertiary-care academic hospital. Semen quality data were analyzed from 114 subfertile men and 60 fertile men. The Student's t test, the Mann-Whitney nonparametric test, and the Pearson correlation coefficient were used for statistical analysis. Sperm with a pyriform head were present in the semen samples of 98% of the subfertile men and 100% of the fertile men; the percentage of this abnormal sperm form was 22 +/- 14.9% in subfertile and 13% +/- 7.8 in fertile men (p <.001); 16% of the subfertile men presented a higher percentage of these abnormal sperm than the normal upper limit. In some subfertile men with a high percentage of sperm with a pyriform head, their subfertility could be attributed to the cause that produces this morphological abnormality. Moreover, morphological abnormalities in the neck and the tail, as also a cytoplasmic droplet, are significantly more frequent in sperm with a pyriform head than in sperm with a normal head.