Chinese healers were extracting hormones from urine by 200 BC
Long before anyone coined the word hormone, Chinese practitioners were isolating sex and pituitary hormones from human urine for medicine, by 200 BC according to one account. Endocrinology, the study of these chemical messengers, now covers everything from diabetes to sleep, and leans on laboratory tests more than almost any other specialty.
Those early Chinese methods included sublimating steroid hormones, and a text dated as early as 1110 describes pulling them out with saponin from the beans of Gleditsia sinensis; gypsum was used too. In Europe, by contrast, Aristotle, Hippocrates, Galen and other classical thinkers favoured humoral explanations of disease, and those ideas held until germ theory and organ-based pathology arrived in the nineteenth century. In 1902 the physiologists Bayliss and Starling gave the classic definition: a hormone is made by an organ, released in small amounts into the blood, and carried to act on a distant organ.
Endocrine glands are ductless, pouring secretions straight into the bloodstream. One hormone can act on several organs, and one organ may answer to several hormones. Feedback loops keep the system steady: thyroid stimulating hormone prompts the thyroid to release its own hormone, and an excess of the latter damps down the former. Chemists sort hormones into three families. Amines such as epinephrine and dopamine derive from the amino acid tyrosine; peptides range from three amino acids to more than 200; steroids are built from cholesterol.
Every organ, including the heart, skin and kidneys, releases some hormones, but clinical endocrinologists concentrate on glands whose main job is secretion: the pituitary, thyroid, adrenals, pancreas, ovaries and testes. The pea-sized pituitary at the base of the brain steers many of the others. Common conditions include diabetes, underactive and overactive thyroid, Cushing's syndrome, Addison's disease and osteoporosis.
Diagnosis often means stimulation or suppression tests, in which a patient receives an agent and blood is then sampled to see how hormone levels respond. A recurring puzzle is telling normal human variation from disease, and scans sometimes turn up incidentalomas, chance findings that may or may not matter. Most endocrine disorders are chronic, so the relationship between doctor and patient can itself be part of treatment. A typical North American endocrinologist trains for about 13 years, counting college, medical school, residency and fellowship.
Source: Endocrinology
