Unlike rats, the adult female hamster is heavier and longer than the male. The small size of the males appears to be dependent on the continuous presence of androgens, since castration before or after puberty results in an immediate acceleration of ponderal and linear growth, which is maintained until the female size is reached. The growth of females is not affected by gonadectomy.
Another sexual dimorphism which is reversed in hamsters in comparison with rats is adrenal weight; males have heavier adrenals than females. Castration reduces both absolute and relative adrenal weights of males to the levels of females. It is possible that the sex difference in growth is mediated through a differential secretion of adrenal hormones.
On the other hand, the sexual dimorphism in pituitary weights of hamsters is similar to rats; females have heavier pituitaries than males. This may reflect a sex difference in the pattern of gonadotrophin secretion, which may be similar in both species.