Endocrine Influences on Hair Growth

Abstract

The differentiation of two aspects of follicular activity is phylogenetically sound and clinically useful. The recurrent cycles of active growth, regression, and rest in the individual hair follicle represent the seasonal moulting cycles of other mammals. The sequence of hair patterns throughout life, which depends on the calibre of the hair produced by each follicle, is linked to the processes of somatic growth, sexual maturation, and ageing. Disturbances of hair pattern are usually produced by excessive or deficient stimulation of follicles by androgens or by somatotrophin, or by genetically determined defects in follicular response. Most such disturbances are incompletely reversed by removal of the endocrine stimulus. Disturbances of hair cycles involve modification of the relative duration of the phases of the cycle and are most characteristically determined by excess or deficiency of glucocorticosteroids or thyroid hormones. They are usually completely reversible. Scientifically planned investigations on hair cycles in man have seldom been undertaken, and conclusions based on comparative studies are tentative. © 1965, British Medical Journal Publishing Group. All rights reserved.