Effects of dietary selenium on sperm motility in healthy men.
The normal values of the spermogram can be defined by analyzing the distribution of sperm characteristics among men whose fertility has been proved (donor candidates, vasectomies). The values proposed on the basis of a study of 294 spermograms are the following: volume - 1.8 ml; concentration - 23 million/ml; total number - 72 million; mobile forms - 35 per cent; normal forms - 32 per cent. The most frequent abnormalities are irregularities of the head and microcephalia. Factors of variability: Different sources of variability must be considered in the analysis of the spermogram. These can be of a technical or a physiological nature. In the later case: the length of abstinence preceding sperm collection is the most important. From 1 to 5 days, there is a linear increase in volume and number, which then stabilizes the situation is the opposite in the case of the percentages of mobile and normal forms, which remain stable for 5 days and then decrease linearly. Age must also be considered to be a source of variability, particularly with respect to the percentages of mobile and normal forms, which decrease after the age of 40. Even when these factors are taken into account, there can be large variations in the spermogram of the same subject from one examination to the next, which necessitates a repetition of sperm examinations before any physiopathological interpretation can be considered. Spermogram results also depend on the period during the year when the collection is made: volume and number are at a minimum in September and at a maximum in March and November, whereas mobility and morphology are better in August and September and less satisfactory in March and April.