India, April 29 -- As a doctor seeing patients with hormonal disorders daily, I feel there is a need for better understanding about hormones. Without hormones, our bodies would descend into chaos: Children wouldn't grow properly, reproduction would falter, hunger and metabolism would go all over the place, and moods would swing wildly. Endocrine glands, once called ductless glands, produce effects distant from their location by pouring hormones directly into the bloodstream. Hormones travel to all parts of our body to regulate vital functions such as metabolism, growth, reproduction, mood, and stress. They are crucial links that transmit messages from the gland of origin to the target organs within minutes, but their effects can last much longer. When they reach their target cells, hormones slot into specific receptors like keys into locks, triggering processes within the cells. An adrenaline rush, something that all of us have experienced, is the body's fight-or-flight response to stress or danger, characterised by a racing heart, rapid breathing, sweating, tremors, and a sharp rise in alertness. This happens because of the sudden release of adrenaline from the adrenal glands, small glands perched on top of the kidneys. Without that surge, we would not respond quickly to danger and might freeze at the very moment we need to act. Another example of a hormone is insulin, which is made in the pancreas. When blood glucose rises after a meal, the pancreas releases insulin. Insulin helps glucose enter muscle and liver cells, where it can be used for energy or stored for later. In fact, every endocrine gland can cause two opposite sets of problems: one caused by too little hormone and the other by too much. For example, hypothyroidism results from underproduction of thyroid hormone, while hyperthyroidism results from excess. The hormone story began with Arnold Berthold's rooster experiment in 1849. In this landmark study, the German scientist showed that transplanting testes into castrated roosters restored aggressive male behaviour and secondary sex characteristics, including the growth of a larger comb. This happened even though the transplanted testes had no nerve connections to the body. The experiment proved that the testes released a substance into the bloodstream that influenced development and behaviour. In 1902, British scientists Bayliss and Starling showed that injecting acidic fluid into the intestine triggered the pancreas to secrete juice, even after the relevant nerves had been cut. This demonstrated that the signal was carried by a chemical messenger, not by nerves. Starling later coined the word "hormone" from the Greek hormao, meaning "to arouse" or "to set in motion". The ability to measure minute quantities of hormones in the laboratory, especially through the work of Rosalyn Yalow in New York in the 1970s, transformed endocrine research. The smooth and coordinated functioning of our endocrine system requires constant communication between glands. The pituitary gland acts like the CEO of the endocrine system. Much like company heads use WhatsApp groups to communicate instantly with their teams, this tiny pea-sized gland at the base of the brain behaves like a group administrator. It sends out messages and the other major glands respond. The anterior pituitary releases several hormones: Growth hormone for growth and repair, thyroid-stimulating hormone to stimulate the thyroid gland, ACTH to signal the adrenals to produce cortisol, FSH and LH for the testes and ovaries to produce sex hormones, and prolactin for breast milk production. The posterior pituitary releases antidiuretic hormone, or ADH, and oxytocin. Pituitary tumours producing too much growth hormone can cause gigantism in children or acromegaly in adults, while deficiencies can cause dwarfism. The pituitary itself is under the control of the hypothalamus, a part of the brain located just above the pituitary. If either the pituitary or hypothalamus starts acting up, the whole system begins to creak. A key feature of the endocrine system is crosstalk between glands. If cortisol levels in the blood surge, they suppress the pituitary's production of ACTH, the hormone that stimulates the adrenal glands to make cortisol. As a result, cortisol production declines. If thyroid hormone levels rise, TSH is suppressed, leading to a drop in thyroid hormone production. This is called negative feedback. It ensures that hormone levels stay within a healthy range and that the system functions in a smooth, coordinated way. It prevents flooding when a particular hormone is being produced in excessive amounts. Hormones are silent messengers, masterfully syncing activities of our body and mind. Stay tuned for deep dives into each of these magic molecules in the months ahead....