Doubtless, this longer growth period of males is one of the reasons for the greater SSD in more favourable environments, as less frequent periods of unfavourable GH- and IGF-1-inhibiting events, i.e. longer periods without illnesses, infections and nutritional detriments can provide additional anabolic time periods with an improved GH and IGF-1 efficiency in males. This evidence concerns the gene GH1 and infection.