In general, the major endocrines, the pituitary, the adrenals, and the thyroid should hypertrophy and hyperfunction during pregnancy.  Should they not, should adverse mechanical circumstances or chemical malfunction prevent, dire effects may follow.  A woman with the closed-in type of pituitary, shut up in a small non-expansile sella turcica, will suffer the most violent headaches, will become fat, will frequently abort.  One whose thyroid cannot rise to the demands of gestation, because of previous disease (like typhoid or measles) which injured her thyroid excessively, may be poisoned by the new elements introduced into the blood by the growing fetus, as it is the job par excellence of the thyroid to render innocuous these poisons.  Of adrenal insufficiency, failure of the adrenals to hypertrophy sufficiently in pregnancy, little is known.  Possibly the corpus luteum, the endocrine formed of the torn egg nest in the ovary, makes up for any deficiency in this respect.  For there is the most curious resemblance imaginable between the cells of the adrenal cortex and those of the corpus luteum, some day to be completely explained.

THE PLACENTAL GLAND

The placenta, an organ and gland of internal secretion newly formed in the uterus, when the fertilized ovum successfully imbeds itself within it, must be considered in any analysis of the transfigurations of child-bearing.  Born with the pregnancy, its life is terminated with the pregnancy, for it is expelled in labor as the after-birth.  Its importance and function as a gland of internal secretion has become known only recently.  Many still doubt and question the accordance of that rank to it.  But feeding experiments with it, in various endocrine disturbances in human beings, have proved its right to the title.

The placenta is created by the fusion of the topmost enlarged cells of the uterine surface and the most advanced cells constituting the vanguard of the growing and multiplying ovum.  These front line invaders interact with the cells in contact with them to make a new organ which serves as lung, stomach and kidney for the embryo, since it is the medium of exchange of oxygen, foodstuffs and waste products between the blood of the mother and the blood of the embryo.  Ultimately it acts, too, as a gland of internal secretion, influencing the internal secretions of the mother, and also those of the embryo.

Settlement of the fertilized ovum in the womb introduces into the system new secretions, new substances which are partly male in origin, since the ovum contains within it the substance of the male sperm which has penetrated it.  This masculine element causes a rearrangement of the balance of power between the endocrines towards the side of masculinity.  They push down the pan of the scale to inhibit the post-pituitary.  So menstruation, the menstrual wave which follows the increasing tide of post-pituitary secretion, is postponed.