Endocrinology

The medical specialty concerned with the endocrine glands and the hormones they secrete, and with diseases of hormonal regulation such as diabetes, thyroid disorders, and adrenal and pituitary disease. Its conceptual foundations were laid in the second half of the nineteenth century by Claude Bernard's theory of internal secretions and Thomas Addison's 1855 clinical description of adrenal insufficiency. The discovery and clinical use of insulin in 1921 and 1922 is the field's most famous single achievement.