We talk so much about hormones nowadays but, unless you studied biology or medicine, you may have only a vague notion of the role they play in your health. So, let’s take a closer look at what hormones are, what their purpose is, and how they help create balance in the body.
What are hormones?
Hormones are tiny molecules that serve as messengers inside the body. Their chemical structures can be divided into peptides, steroids and amines. Together with the glands that produce them, the blood that transports them, and the receptors on the cells of the target tissues that carry out their instructions, they form the endocrine system, which works closely with the central and peripheral nervous system and the immune system.
What do hormones do?
Our bodies produce a long list of hormones and hormone-like messengers, and we continue to discover new ones and learn more about their functions and regulation. The most important organs producing hormones are the hypothalamus and pituitary, just below the brain, the thyroid, parts of the pancreas, ovaries, testicles and adrenals. Textbooks over 1000 pages long have been written about the endocrine system, so please forgive me if I simply things a little to get you started. Let’s go over the major sites of hormone production and get a quick handle on the purpose of their most important hormones.
The hypothalamus and pituitary
The hypothalamus is part of the brain, and the pituitary is an appendix to the brain directly attached to it. It sits in the sella turcica, a little saddle deep inside your skull, just below the brain. The pituitary is also referred to as the master gland because it sends signals to other endocrine tissues in the body, telling them how much of their respective hormones to produce. The hormones produced by the anterior pituitary are growth hormone (GH), ACTH, which regulates production of cortisol in the adrenals, thyroid stimulating hormone (TSH), follicle stimulating hormone (FSH) and luteinizing hormone (LH), as well as prolactin. The production of pituitary hormones, in turn, is regulated by hypothalamic hormones produced in response to feedback from the body’s circulating hormones. In other words, when the stimulating hormones produced by the pituitary have generated a sufficient response in the target glands, the hormones produced by these glands will circulate through the blood and signal the hypothalamus that the level has gone up, so the production of the corresponding stimulating hormones can now be turned down. So smart!
The thyroid and parathyroid
The thyroid is a butterfly-shaped gland in front of your throat. It produces and stores thyroid hormones (T4 and T3), essential hormones for the health of all body tissues and functioning. They regulate the body’s temperature, metabolism and heart rate, as well as many other more subtle functions. Low thyroid function can contribute to infertility. Attached to the thyroid are four small parathyroid glands which produce a hormone that regulates the amount of calcium circulating in the blood or stored in the bones.
This organ located next to the stomach has two functional parts, one exocrine the other endocrine. The endocrine part is where our insulin is produced. Insulin is indispensable for our survival because it facilitates the movement of glucose from our bloodstream into the cells of the body. Insulin production and sensitivity are central topics for people with diabetes, metabolic syndrome and PCOS.
They are attached to the top of each kidney. The adrenal cortex (the outer layer) has three functional zones and produces aldosterone, cortisol and androgens. The outer zone, called the zona glomerulosa, produces a mineralocorticoid named aldosterone, which plays an important role in (long-term) regulation of blood pressure. The next one is called zona fasciculata, which is where glucocorticoids such as cortisol are produced. Cortisol, of course, is well known for its role in our stress response. Lastly, the innermost layer, the zona reticularis, produces androgens including precursors to testosterone.
Women have ovaries, men have testes. These glands respond to follicle stimulating hormone and luteinizing hormone produced by the pituitary (described above). The ovaries make an estrogen called estradiol, which makes several follicles and the eggs contained within grow each month, it promotes thickening of the endometrium, the inner lining of the uterus, and is responsible for the development of female characteristics in girls during puberty. Once an egg has ovulated, the follicle itself turns into a gland producing progesterone, a hormone balancing the effects of estrogen and important for sustaining pregnancy should conception occur.
The testes of men are the site of testosterone production (in the Leydig cells), which is an androgen stimulating the development of male characteristics in boys, maintaining libido, muscle strength and bone density. Note that a woman’s ovaries also produce a smaller amount of testosterone, so it is not an exclusively male hormone. Conversely, men also produce small amounts of estrogens. The important question is, Are these hormones produced in the right amounts to be in balance?
The balance of hormonal production is quintessential for our health and wellbeing. The production of the various hormones is affected by our genetics, age, exposure to daylight, temperature and other environmental factors, especially toxins. Artificial chemicals in our food supply, household products and cosmetics may function as endocrine disruptors and disturb our hormonal regulation in worrisome and lasting ways.
Our hormone production is also affected by the availability of nutrients that form the building blocks of hormones, for example cholesterol as a precursor for steroid hormones, including sex hormones. How well our hormones work also depends on how sensitive our cells are to the messages they deliver. Our cells can upregulate and downregulate receptors on the cell surface. Receptors are like docking stations that hormones need to deliver instructions to the cells.
Lastly, the effects of hormones can be altered by how competently our liver metabolizes hormones for elimination from our bodies through the urine and stool. Even your gut bacteria are involved in regulating, for example, healthy levels of circulating estrogens.
While this may seem like a lot of complicated information, let me assure you that we’re only just scratching the surface of how hormones work. Luckily, a healthy body is so intelligent and well regulated that all these messages and their effects run like clockwork. You don’t have to lift a finger to make it all work. However, your hormonal regulation can go off the rails, sometimes suddenly but more often very gradually, if you don’t take care of your health by eating well, resting enough and keeping stress at bay. Many pharmaceutical drugs can also negatively affect your endocrine system, just like a whole range of industrial chemicals can.
© 2020 Christiane Siebert