Hormones rule your entire life. They control your growth, weight, metabolism, fertility and water balance. They initiate and regulate life changes like puberty and menopause. They have a hand in the speed of ageing, whether you want sex or not, even whether you enjoy it and who will fall in love with. Their effects may occur in seconds and be over in a flash, or take months or years. They control your mood and other emotions too, especially those that grip you in the most visceral way-fear, anger, and love.
Hormones for communications
Hormones are slaves of one of body's two internal communication systems. The nervous system carries message from the brain that are transmitted throughout the body by electrical stimuli the hormone system, more correctly known as endocrine system, is much slower, and uses blood as it's medium for communication and hormones as messengers. To compare these two systems is like to compare a high speed rail network with that of canals.
Even the simplest of animals need to communicate what is going on outside the body to each of its cells inside. Without some for of internal communication, how could it coordinate a response that would ensure survival? How could the animal function as one organism, without some means of enabling all its constituent parts to talk to each other?
Chemical messengers work by travelling to a cell with an instruction to do something. Once they reach their target, the molecules of hormones find unique docking bays, called receptors, and deliver their message. The master gland is actually the brain itself, especially a part called hypothalamus, from which the pituatory dangles by a little stalk and that lot of organs act as endogenous glands, including the placenta and gut, and many tissues including muscles, produce hormones. Hormones are so many that today they are counted in hundreds.
We have not say in the genes we acquire, which contain the instructions for the various elements of the endocrine system. Hormones are like breathing in that they work independently of conscience thought. But in another sense, we are capable of controlling them. Our actions drive them. They are the body's response to our conscience activities, whether it is running, eating or falling in love.
System can go wrong
Given the complexity of the endocrine system, it is perhaps not surprising that it can go wrong. Such conditions include gigantism, caused by an excess of growth hormone, the growth of a big lump in the neck called goitre caused by shortage of thyroid hormone, or wasting disease called diabetes, caused due to shortage of insulin from pancreas.
Hypothalamus as a command unit
Hormones send messages through blood. At any one time there are thousands of messages in the blood being carried by hormones. The endocrine system is one of the constant changes. The master controller hypothalamus in brain, releases two types of regulating hormones, releasing one and inhibiting ones. They act on pituatory. The hypothalamus and pituatory function together as one unit, known as hypothalamus - pituatory axis.
The function of the hypothalamus is as a command unit. It keeps on receiving input from the brain and then sending out appropriate messages, sometime by nerve impulse for fast response and sometimes by employing hormones via the pituatory gland for a slow response. There is also a third way by using nerve to stimulate the production of hormones. Three endocrine systems secret their hormones only in response to nerve stimulation resulting in a chain reaction. These three glands are (i) Adrenal medulla, producing adrenaline and noradrenaline which function as chemical messengers causing body to flight, (ii) Pineal gland producing melatonin which helps to induce sleep and, (iii) Posterior pituatory producing vasopressin and oxytoin.
Hormones in groups
Hormones tend to come in pairs or groups of three. These are the hormone itself and a mate (or two) involved in the release or inhibition. Quite often hormones regulate themselves, in that when a certain concentration is reached in the blood, the hormones themselves prevent more being released.
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Hormones produced in cycles
There are about 20 major hormones. Besides, muscles and tissues act as endocrine glands. Fat cells produce hormone leptin. Placenta also produces some hormones for its own use. Many hormones are secreted in a cyclical fashion, one in a month alongwith female reproductive organs. Gonadotropins releasing hormone is released in bursts every ninety minutes or so. Hormone production varies during a twenty four hours period, e.g. testosterone levels are highest in the morning. Growth hormone and the milk producing hormone prolactin are released during sleep. Therefore, different hormone measurements at a particular time are misguiding and usually urine collection over a twenty four hours period will be required to give an accurate assessment of hormone levels.
Messages must reach cell nucleus
All hormones have to reach individual cells. The cell surface is covered with receptors, which are like docking bays. They are needed because many hormones cannot pass through cell membranes to deliver the messages to nucleus of the cell. The receptors set up a chain reaction to reach the message to cell nucleus. Receptors are highly selective. They provide a specific docking bay for every hormone. There is an exception to the way docking works. Steroid hormones, unlike other hormones, are fat-soluble. Cell membranes being made of fat, they are able to mix with the fatty cell membranes and thus enter the cell to reach the message to nucleus.
Hormone types
Hormones can be divided into three main types. The majority of them are proteins. Some others are steroid made from cholesterol and finally the ones which are derived from tyrosine, an amino acid. Recently, three other groups of so called quasi-hormone status have been discovered. These are prostaglandins, cytokines and nitric oxide. Endocrine system does not work in isolation, but is connected to other body systems. It has particularly close relationship with immune system.
So hormones are truly slaves, though extraordinarily powerful. Hormones are now available to treat virtually all the hormone deficiency diseases. Most of the hormones are isolated in pure state by using bioengineering techniques. However, hormone administration therapy for corrective treatment is yet under experimentation. Attempts are being made to make these therapies reliable, without side effects, in providing guaranteed and complete cure from the concerned ailment to the patient.
(The author is a technical consultant based in Mumbai.)