The Hypothalamic-Pituitary-Adrenal Axis: A Brief History.

The hypothalamic-pituitary-adrenal (HPA) axis is central to homeostasis, stress responses, energy metabolism, and neuropsychiatric function. The history of this complex system involves discovery of the relevant glands (adrenal, pituitary, hypothalamus), hormones (cortisol, corticotropin, corticotropin-releasing hormone), and the receptors for these hormones. The adrenal and pituitary were identified by classical anatomists, but most of this history has taken place rather recently, and has involved complex chemistry, biochemistry, genetics, and clinical investigation. The integration of the HPA axis with modern neurology and psychiatry has cemented the role of endocrinology in contemporary studies of behavior.

HANS SELYE AND THE STRESS RESPONSE: FROM "THE FIRST MEDIATOR" TO THE IDENTIFICATION OF THE HYPOTHALAMIC CORTICOTROPIN-RELEASING FACTOR.

Selye pioneered the stress concept that is ingrained in the vocabulary of daily life. This was originally build on experimental observations that divers noxious agents can trigger a similar triad of endocrine (adrenal enlargement), immune (involution of thymus) and gut (gastric erosion formation) responses as reported in a letter to Nature in 1936. Subsequently, he articulated the underlying mechanisms and hypothesized the existence of a "first mediator" in the hypothalamus able to orchestrate this bodily changes. However he took two generations to identify this mediator. The Nobel Laureate, Roger Guillemin, a former Selye's PhD student, demonstrated in 1955 the existence of a hypothalamic factor that elicited adrenocorticotropic hormone release from the rat pituitary and named it corticotropin releasing factor (CRF). In 1981, Wylie Vale, a former Guillemin's Ph Student, characterized CRF as 41 amino acid and cloned the CRF1 and CRF2 receptors. This paves the way to experimental studies establishing that the activation of the CRF signaling pathways in the brain plays a key role in mediating the stress-related endocrine, behavioral, autonomic and visceral responses. The unraveling of the biochemical coding of stress is rooted in Selye legacy continues to have increasing impact on the scientific community.

The legacy of Hans Selye and the origins of stress research: a retrospective 75 years after his landmark brief "letter" to the editor# of nature.

Hans Selye's single author short letter to Nature (1936, 138(3479):32) inspired a huge and still growing wave of medical research. His experiments with rats led to recognition of the "general adaptation syndrome", later renamed by Selye "stress response": the triad of enlarged adrenal glands, lymph node and thymic atrophy, and gastric erosions/ulcers. Because of the major role of glucocorticoids (named by Selye), he performed extensive structure-activity studies in the 1930s-1940s, resulting in the first rational classification of steroid hormones, e.g. corticoids, testoids/androgens, and folliculoids/estrogens. During those years, he recognized the respective anti- and pro-inflammatory actions of gluco- and mineralocorticoids in animal models, several years before demonstration of anti-rheumatic actions of cortisone and adrenocorticotrophic hormones in patients. Nevertheless, Selye did not receive a Nobel Prize, which was awarded in 1950 to the clinician Hench and the two chemists who isolated and synthesized some of the glucocorticoids. Nonetheless, Selye was internationally recognized as a world authority in endocrinology, steroid chemistry, experimental surgery, and pathology. He wrote over 1500 original and review articles, singly authored 32 books, and trained 40 PhD students, one of whom (Roger Guillemin) won a Nobel Prize for isolating the hypothalamic releasing factors/hormones. Here, we consider the main implications of his first article launching the biological stress concept and the key ideas and problems that occupied him. Selye considered "Stress in heath and disease is medically, sociologically, and philosophically the most meaningful subject for humanity that I can think of".

Adrenocorticotropic hormone, melanocyte-stimulating hormone, and the melanocortin receptors: revisiting the work of Robert Schwyzer: a thirty-year retrospective.

In 1977 Dr. Robert Schwyzer wrote the review ACTH: A Short Introductory Review, which provided a reference point for current structure/function studies on the interactions between adrenocorticotropic hormone and alpha-melanocyte-stimulating hormone and the melanocortin receptors. This mini review will evaluate how the predictions made in the 1977 review have held up and also propose a mechanism to explain the ligand selectivity properties of the melanocortin receptors.

Teaching glucocorticoid negative feedback and adrenocortical regulation using a classic paper by Dr. Dwight Ingle.

The American Physiological Society (APS) Legacy Project and its accompanying Essays on APS Classic Papers have allowed the scientific community on-line access to the entire collection of APS publications since their inception in 1898 (http://www.the-aps.org/publications/legacy/ and http://www.the-aps.org/publications/classics/). The availability of the classic physiological studies provides a unique teaching opportunity. The classic paper of Dr. Dwight Ingle represents just such a study. Dr. Ingle demonstrated that, using only purified extracts of the pituitary (ACTH) and adrenal cortex (corticosterone) and hypophysectomized rats, he could establish several of the basic principles of the control of adrenal function and glucocorticoid negative feedback that are now standard teaching material in endocrinology. An annotated figure from Dr. Ingle's paper is provided, which, when assigned to undergraduate or graduate students, will allow discovery learning. Furthermore, the brilliance and imagination of the physiologists of the last century are highlighted, which allows an appreciation of the seminal work of our predecessors.

H.H. Dale and the London Centre for WHO standards--some milestones of the early years.

Henry Dale, a Nobel laureate and statesman of science, helped to organize the meetings in 1923 and 1925 to set up international standards for insulin and other biologicals. He made the National Institute for Medical Research one of the two world centres for standards. Some milestones in the work of the London centre are described: (i) the first standards; (ii) vitamins and hormones; (iii) WHO standards for many antibiotics; (iv) the provision of an international working standard for ACTH; (v) the old and new methods of ampouling; (vi) the impact of research and immunoassay on the need for standards; and (vii) the special ECBS sessions for endocrinology and haematology. Dale tells how he had to preserve the first batch of insulin for use as the standard instead of for treatment.

An historical review of rheumatoid arthritis treatment: 1948 to 1952.

OBJECTIVES: The early responses by practicing physicians to the discovery of the effect of cortisone (compound E) and adrenocorticotropic hormone (ACTH) on acute rheumatoid arthritis in 1948 and their reactions to the drugs' scarcity have been reviewed. METHODS: Review of the relevant literature in American, British, and European medical journals and some newspapers. RESULTS: Whereas the effect of the compound E and ACTH was stunning, their scarcity made them unavailable to most physicians. Nevertheless, practicing physicians took a lively interest in the new therapy, as witnessed by the large number of letters with comments and questions to professional journals from all over the world. As expected, most of these were about attempts to find a substitute for cortisone or a way to release it endogenously to a sufficient degree. A few alternative therapies were suggested too, some quite unorthodox. A lively interest was shown by the general public. CONCLUSIONS: No alternative therapy recommended to treat acute rheumatoid arthritis in lieu of cortisone proved to be effective. The era of scarcity was ended by the discovery of a more efficient method to manufacture cortisone.