The part played by the endocrine system in psychiatric illness is still controversial. Mental disorders may occur at the menopause or in the Puerperium, accompany thyroid or pituitary dysfunctions, or appear in adrenocortical diseases. Castration in men and women may be followed by marked personality changes. But often there are little or no mental changes, and there is certainly no clear-cut mental accompaniment of specific endocrine diseases. It is probable that mental symptoms, when they do occur, are dependent upon the basic personality structure, not upon a particular diseased gland. It is also likely that glandular dysfunction in turn can be brought about by mental stress or disorder. In other words, the two systems function together and should not be artificially separated.