How glands affect personality

How glands affect personality by Grace Kinckle Adams is a popular scientific publication written in the early 20th century. It explores how the endocrine glands influence growth, emotion, and temperament, proposing that differences in gland activity underlie many variations in personality.

The book first defines personality as the integrated sum of physical, mental, and emotional traits, then explains how knowledge of glands comes from clinical observation and animal experiments. It distinguishes exocrine from endocrine glands and details the roles of the latter: the thymus and pineal guide childhood; the sex glands’ interstitial cells trigger secondary sex traits; the thyroid supports growth, metabolism, and mental tone; the parathyroids sustain life; the pituitary governs skeletal growth and muscular tone; and the adrenals mobilize the body for emotion and stress. Adams surveys abnormalities—precocious or delayed puberty from pineal or thymic shifts; thyroid disorders such as cretinism, myxedema, and exophthalmic goiter; pituitary-driven gigantism, dwarfism, and adult obesity; and adrenal-linked fatigue, high-strung states, precocious puberty, and virilism. She concludes by applying these insights to everyday personalities, arguing that subtle excesses, deficits, and compensations among glands help explain common physiques and temperaments—while emphasizing that most people reflect the shifting balance of the entire endocrine system rather than any single gland.