META - FACULTY: THE ENDOCRINE SYSTEM
The endocrine system can best be described as a meta-faculty, because the real job of the endocrine glands, working together as a whole, is to unite and integrate all the major faculties and organ systems of the body into one seamless whole. These ductless glands secrete their hormones directly into the bloodstream, utilizing the Vital Faculty's circulatory network to penetrate throughout the organism and reach any target, local or distant.
Nevertheless, some endocrine glands pertain more to a single faculty or organ system, whereas others interface between multiple systems, and are multifaceted in their functions. As a whole, the function of the endocrine system is to integrate the response of the whole organism to its environment, from short term nervous and immunological responses to long term growth and developmental changes.
A precise knowledge of the endocrine glands, their secretions and how they function is a comparatively recent discovery of modern medicine. Nevertheless, the precepts of Greek Medicine can be applied to approach the endocrine glands and their physiology from a traditional holistic perspective.
The Endocrine Glands and the Radical Moisture
According to Greek Medicine, the basic stuff of the endocrine glands and their secretions is the Radical Moisture, also called the vital sap, marrow or essence of the organism. It could also be called the hormonal essence. Throughout the individual's lifetime, the Radical Moisture feeds and nourishes the organism on a deep and fundamental level, guiding it through the slow changes of growth, development and maturation. Its long slow decline through middle age and beyond is one of the central factors responsible for the aging process.
Constitutionally, individual endowments of the Radical Moisture vary greatly, both in quantity and in quality. Gametes, genes and heredity are one aspect of the Radical Moisture, contributed equally by both parents and passed on from generation to generation. Like any other organ, tissue or part of the body, the endocrine system as a whole, or individual glands, may be stronger or weaker, larger or smaller, as endowed by hereditary or constitutional factors.
After birth, the Radical Moisture, through the action of the Innate Heat of metabolism and the Vital Faculty, begins to unfold like the petals of a rose in the hot midday sun. What was potentially contained in seed form in one's inherited endowment of the Radical Moisture begins to manifest and be activated as the growth and developmental changes of youth, puberty and adolescence unfold. Imbecility, retardation and other growth and developmental disorders are due to either quantitative or qualitative defects or deficits in the Radical Moisture.
In puberty and adolescence come the secondary sexual changes in both sexes. In men, the voice deepens, the penis enlarges, facial hair appears, and the muscles grow and develop. In women, pubic hair appears as the female genitals grow and develop; also, the hips widen, and the breasts grow and develop. These secondary sexual characteristics are due to the flowering and proliferation of the Radical Moisture, which now becomes plentiful enough to pass on through the reproductive process and the creation of offspring.
After reaching the apex of a full flowering in young adulthood, the Radical Moisture begins to decline in middle age and beyond, as the very same Innate Heat of metabolism that caused its blossoming and proliferation now begins to consume it. Modern medicine confirms this fact, since there is a universal, global decline in all the endocrine hormones and secretions as we age. The Radical Moisture begins to dry up; accordingly, aging is essentially a drying out process, as the flesh begins to waste and atrophy and the skin starts to wrinkle and wither.
Although a universal, gradual decline in the Radical Moisture is responsible for the aging process, this decline can be extended and made even more gradual if we treat our endocrine glands right to conserve our Radical Moisture. This includes sexual chastity and moderation, stress management, eating right, getting adequate sleep and rest, and generally living a balanced and well-regulated life. Certain herbs and tonics can be used to enhance or replenish the Radical Moisture to a limited extent, and are therefore useful in life extension and retarding the aging process, but most important are the dietary and lifestyle factors listed above.
The Endocrine Glands and the Spinal Energy Centers, or Chakras
To the classical Greek philosophers, physiologists and physicians, the ductless endocrine glands were indeed a mystery. But what the hermeticists and other esoteric philosophers noticed was that many, if not most of them, were located at or near certain subtle Spinal Energy Centers, or chakras:
Koruphe (Crown Center) - Pineal Gland
Enkephalos (Brow Center) - Pituitary / Hypothalamus
Trachelos (Throat Center) - Thyroid Gland
Phrenes (Heart Center) - Thymus Gland
Gaster (Gastric Center / Solar Plexus) - Pancreas
Gonades (Generative Center) - Gonads
Hieron Osteon (Root Center) - Adrenals
They then reasoned that the function of the associated endocrine gland must have something to do with the spiritual, psychological, psychosomatic and physiological functions attributed to the chakra, or energy center.
Plato saw the Spinal Energy Centers, or chakras, as being the subtle organs of the Soul in establishing dominion over the mind and body. The Soul, said Plato, manifests in three forms, or exists at three different levels of expression.
The highest level of Soul expression Plato termed Nous or Logos; the highest form of the Soul he called the Psyche, or Immortal Soul. The Psyche has its seat at the Enkephalos, or Brow Center; its associated endocrine gland is the Pituitary / Hypothalamus, which is the master gland of the endocrine system.
The middle or intermediate level of Soul expression Plato termed Thymos; its middle level of Soul expression was what he called the Mortal Soul, which masterminded the body and its life expression through the Vital Faculty. Its seat is at the Phrenes, or Heart Center; its associated endocrine gland is the Thymus gland.
The lowest and most primitive level of Soul expression Plato termed Epithymia, which has to do with our basic survival drives and instincts. This most primitive level has its seat at the Hieron Osteon, or Root Center; its associated endocrine glands are the Adrenals.
When we look at things from the perspective of the body and its basic constitutional strength, stamina, resilience and resistance to disease, then the most important chakra is the Root Center, and the most important endocrine glands are the Adrenals. The Adrenals form the basic energetic support or foundation for the entire organism.
The Spinal Energy Centers or chakras, the ancient philosophers and physicians recognized, were places where the Radical Moisture, the vital sap of the organism, or the hormonal essence, was especially abundant. Wherever there were large concentrations of this vital essence, this Radical Moisture, there was also a high level or concentration of psychic or spiritual energy.
As physical manifestations of this abundant Radical Moisture at the chakras, there was often an abundance of hair on the body, as in the head hair over the Crown Center. Also, pubic hair and the appearance of the secondary sexual changes of puberty and adolescence that were mentioned earlier center around the Spinal Energy Centers, or chakras.
For more information on Greek Medicine and the chakras, please read my Greek Chakras page under Basic Principles.
The Endocrine Glands
Each endocrine gland is involved with regulating certain physiological functions through one or more of the Four Faculties, and through various organ systems of the body. The functions of the various endocrine glands can often be seen in their anatomical form, structure, or location in the body; in Nature, form follows function.
The nature and temperament of an endocrine gland and its hormonal secretions can also be analyzed according to the traditional physiological principles of Greek Medicine. Each endocrine gland, and each hormone has its own nature and temperament.
What follows is a description of the various endocrine glands, from head to toe, according to Greek Medicine:
The Pineal gland, or body, has been, and continues to be, the most mysterious of the endocrine glands, although a lot more is known about it now. Its main known secretion is melatonin, which plays an important part in regulating our sleep / wake cycles, and in enhancing the restorative nature of sleep and dreams.
Melatonin is closely related to serotonin, which supports our mood levels and fights depression. If serotonin levels are low, so will be melatonin, usually.
Melatonin production increases during the dark hours of the day to bring on drowsiness and sleep. This sedative action makes melatonin's effect predominantly Phlegmatic. Increasing levels of darkness are transmitted from the eyes to the Hypothalamus, and from there to the superior cervical ganglia of the Sympathetic Nervous System, which then stimulate the Pineal gland to secrete melatonin.
The Pineal gland is located behind the two cerebral hemispheres, behind and slightly superior to the Hypothalamus, which lies underneath the brain at the center of the cranial cavity. In yogic philosophy, this is the approximate location of the Bindu chakra, which has a lunar nature and influence, and a restorative, anabolic effect.
Pituitary / Hypothalamus
In the center of the cranial cavity, right in the middle of the underbelly of the brain sit the Pituitary and Hypothalamus. This location puts it right behind the Brow Center, or Third Eye chakra, which Plato considered to be the seat of the Psyche, or Immortal Soul.
In ancient times, the exact function of the Pituitary / Hypothalamus complex was unclear; many classical physicians felt that the Pituitary, sitting between the brain and the interior nasal cavity, might be a receptacle and escape valve for excess phlegm from the brain, which allowed it to flow down into the nose and pharynx as nasal discharge, catarrh and post nasal drip.
But now, we know that the Pituitary and its control module, the Hypothalamus, are the two master glands of the endocrine system, which regulate and control the activity of all the other glands. And so, directly or indirectly, there is no faculty or organ system that the Pituitary and Hypothalamus do not affect in some way. Just as Plato's Psyche, or Immortal Soul controls and directs the mind and body as its vehicles for expression, so do these two master glands control the whole endocrine system, and through it the whole bodymind complex.
The Pituitary gland secretes eight different hormones, with a wide variety of different target organs and effects, and hence a wide array of differing natures and temperaments. But overall, the general character and influence of the Pituitary is anabolic and nutrient enriching, energy conserving and growth promoting. These attributes, plus the Pituitary's proximity to the brain, a Phlegmatic organ, tip the scales to make its overall nature and temperament Phlegmatic. However, the natures and effects of the individual hormones released by the Pituitary are as follows:
Human Growth Hormone (HGH): Sanguine - anabolic, nutrient enriching, growth promoting.
Thyroid Stimulating Hormone (TSH): Choleric - stimulates the production and release of Thyroid hormones, which raise the basal metabolic rate, increasing both the Innate Heat of the Vital Faculty and the Metabolic Heat of the Natural Faculty.
Adrenocorticotropic Hormone (ACTH): Sanguine - stimulates the release of adrenocortical hormones, principally the glucocorticoids, enriching the nutrient content of the blood and its caloric potential.
Prolactin: Phlegmatic - stimulates the production of milk, a white, Phlegmatic exudate and anabolic, nutrient dense food in the breasts of nursing mothers.
Lutenizing Hormone (LH) and Follicle Stimulating Hormone (FSH): Phlegmatic / Sanguine - control the female reproductive cycle and ovulation, which make conception, pregnancy and motherhood possible; tied in with the monthly lunar cycle.
Antidiuretic Hormone (ADH): Phlegmatic - conserves water and clear Phlegmatic fluids in the organism by preventing their excessive or undue release by the kidneys.
Oxytocin: Melancholic / Phlegmatic - its Nervous/Melancholic effect is to stimulate uterine contractions in labor, expelling the foetus; its Phlegmatic function is to stimulate the secretion of milk in lactation.
If one looks at the Pituitary gland from an astrological perspective, it seems to be quite like a central Sun, controlling its various target organs and glands, which are like its orbiting planets, through its various hormonal secretions. Psychosomatically, a mental attitude of confidence, calm and poise is most conducive to the balanced, harmonious functioning of the Pituitary.
The Thyroid is a butterfly shaped gland that straddles the Adam's apple in the hollow of the throat. It is the endocrine gland associated with the Throat Center or chakra, and is psychosomatically connected with issues involving speech, communication, and speaking one's truth.
Physiologically, the Thyroid is like the master thermostat of the organism. It sets the Innate Heat of the Vital Faculty through the basal metabolic rate, which is the basic speed and heat level of cellular metabolism. This also determines how quickly carbohydrates and calories are burned for energy.
In terms of the Natural Faculty, the Thyroid also controls and sets the rate of liver metabolism, or its Metabolic Heat, which concocts all the humors. If Thyroid output is low, the liver will get slow and sluggish, toxins will accumulate, and bile production and metabolism will suffer, leading to constipation and a sluggish digestion and bowels.
Metabolically, the basic influence of the Thyroid and its hormone, Thyroxin, is hot, catabolic and Choleric. The more Thyroxin released, the hotter and faster the metabolic rate and the burning of calories for energy; conversely, the lower the Thyroid output, the lower or slower the metabolic rate, and the colder the body. The ideal is to have the Thyroid thermostat set just right.
Hypothyroidism, or low Thyroid output, is distinguished by several outward signs: myxedema - water retention with puffiness of the skin, facial edema and deep, sunken eyes. Hypothyroidism is basically a Phlegmatic condition, with a low Innate and Metabolic Heat, hypofunctioning kidneys and a consequent retention of bodily fluids. But it is also a condition of poor elimination and liver function, with toxic buildup and obstinate constipation. Hypothyroidism is quite common and widespread, and many people have borderline low Thyroid output. Thyroid function can also be compromised or injured by heavy metals, radioactivity and environmental toxins.
Hyperthyroidism, or high Thyroid output, is distinguished by exopthalmia - large, protruding "bug eyes". Excessive Thyroid hormone floods the body and ratchets up the metabolism into overdrive. To the extent that Hyperthyroidism is a hot, hypermetabolic state, it could be called a Choleric condition, but it's not that simple. More importantly, Hyperthyroidism is an aesthenic Nervous/Melancholic condition, with high nervous stress and tension, a thin furtive nervous sweat, insomnia and a rapid consumption or wasting away of the Radical Moisture and the bodily tissues. It isn't as common and prevalent as Hypothyroidism, but it's quite a problem when it does occur.
The Melancholic character of the Thyroid is underscored by the fact that it is often metabolically challenged in those of a Melancholic temperament. Psychosomatically, the Thyroid is also associated with rigid, dogmatic attitudes and reclusive, misanthropic tendencies.
The Parathyroid glands are four little buttons that sit on the backside of the Thyroid. They secrete Parathyroid hormone, which helps regulate calcium metabolism. When blood calcium levels fall too low, Parathyroid hormone is released, which takes calcium out of the bones and puts it back into the blood. When blood calcium levels get too high, Calcitonin is secreted by the parafollicular cells of the Thyroid to take calcium out of the blood and put it back into the bones, which act as a calcium bank, or reservoir, for the whole organism.
Together, the Thyroid and Parathyroid glands regulate calcium metabolism. This fact strengthens their overall Melancholic nature and temperament, since calcium is one of the Earth minerals whose metabolism is traditionally associated with black bile.
Plato believed that the Heart Center, or chakra, was the seat of the Mortal Soul, which he called Thymos. Moved by strong sentiments, passions and emotions, the Mortal Soul is all fight and desire, expressing itself as the will to live.
In Greek Medicine, this Thymos that fights for our will to live is also the immune force of the organism, and the essence of the Vital Faculty. The Thymos powers the immune response.
Psychosomatically, positive, noble, uplifting thoughts and emotions that strengthen the heart and its Vital Spirits also strengthen the Thymus gland, and with it the Thymos and the immune response. Conversely, negative, ignoble, degrading or constrictive thoughts and emotions that weaken the heart and its Vital Spirits also weaken the Thymus gland, as well as the Thymos and immune response. Above all, a spiritual attitude of Self love and self acceptance is important for the healthy, optimum functioning of the Thymus gland.
Since the Thymus gland, and hence immunity, thrive with a hopeful, positive, optimistic attitude, the Thymus gland is Sanguine in nature. In keeping with its Sanguine character, the Thymus gland is usually big throughout the Sanguine growing years of childhood and youth, and then shrinks and atrophies in adulthood and beyond, for reasons that aren't entirely clear.
The Pancreas, sitting right underneath the stomach and behind the navel, is the endocrine gland associated with the Gastric Center, or Solar Plexus. This chakra is the seat of what Plato called the Appetitive Soul, whose chief concern is to make sure that the body gets fed. And so, the chief endocrine function of the Pancreas is to regulate the blood levels of glucose, the main carbohydrate food and energy currency of the organism.
Since the Natural Faculty's job is to feed the organism, the Pancreas, in both its digestive and endocrine functions, pertains most centrally and directly to the Natural Faculty, and works closely with the liver, its principal organ, to regulate blood sugar levels. But since glucose, or blood sugar, is the main caloric fuel for cellular metabolism as well, the Pancreas also interfaces with the Vital Faculty.
The Pancreas regulates blood sugar through two important hormones that work on the blood in opposite yet complementary ways to maintain a balance, or homeostasis:
Insulin, whose effect on blood sugar is catabolic, or consuming, and Melancholic, or depleting. When blood sugar levels get too high, insulin is released by the Pancreas, which facilitates the uptake or absorption of blood sugar by the cells to be burned for energy.
Glucagon, whose effect on blood sugar is anabolic, enriching and therefore Sanguine. When blood sugar levels get too low, glucagon is released by the Pancreas, which signals to the liver to convert more glycogen into glucose and release it into the bloodstream, increasing the caloric potential and energy availability.
Since blood sugar regulation is such an important and crucial concern for the health and wellbeing of the entire organism, many other organs and endocrine glands play secondary or supporting roles as backup mechanisms in this vital process. And so, blood sugar problems or imbalances, whether high, as in various types of diabetes, or low, as in hypoglycemia, seldom involve just pancreatic secretions of insulin and glucagon alone, but affect other organs and glands as well. The main ones are as follows:
The liver acts as the main storage bank or reservoir for glucose, in the form of glycogen, for the whole organism. When blood sugar is too high, the liver converts the excess glucose into glycogen; when it is too low, glucagon signals to the liver to convert it back into glucose and release it into the bloodstream. If the liver is toxic or damaged, its capacity to balance or moderate blood sugar levels through the storage and release of glycogen may be reduced or compromised, which tends to destabilize or raise blood sugar levels.
Diabetes usually involves insulin failure by the Pancreas. In type I diabetes, which is often congenital, the problem is usually a deficiency or lack of adequate insulin production. In type II diabetes, insulin is produced, but due to various factors, often linked to dietary abuse and consequent weight gain, insulin resistance develops, which makes insulin less effective in doing its job of increasing glucose uptake or absorption and utilization by the cells. In both types, the end result is the same: high blood sugar.
Hypoglycemia, or low blood sugar, usually involves hyperinsulinism, or the secretion of too much insulin by the Pancreas. Usually, too many sweets are eaten, causing a blood sugar rush; the Pancreas then over-reacts, dumping too much insulin into the bloodstream, which leads to too much cellular uptake of glucose and a consequent plummeting of blood sugar to dangerously low levels. The blood sugar roller coaster ride of hypoglycemia often progresses, as it gets more chronic, into the insulin resistance that's usually responsible for type II diabetes.
The Adrenal glands often jump into the act as heroic rescuers of blood sugar levels when they get dangerously low. Adrenaline can raise blood sugar levels over the short term as part of the "fight, fright, flight" response to stress, which in this case is blood sugar stress. If blood sugar instability due to stress gets too chronic, the adrenocortical hormones often kick in, particularly the glucocorticoids, which raise blood sugar levels. Adrenocortical hormone involvement is often a secondary contributing or aggravating factor in type II diabetes.
According to Greek Medicine, the sweet taste is not only the most nourishing and anabolic, but it's also the most quickly assimilated and utilized. Eat a candy bar or down a little soda pop and your blood sugar levels are skyrocketing within minutes. The excessive consumption of sweets and sugar is like pouring gasoline on the body's metabolic fire; it flares up suddenly, but then quickly dies out. Therefore, it behooves us to use the complex carbohydrates of whole grains, tubers and root vegetables as our main energy source, since they are burned or metabolized in a stable, balanced manner by the organism.
Sitting as caps or crowns on top of each kidney are the Adrenal glands. Their core function is to act as energetic supports to enhance several important physiological functions, and help the organism fight fatigue and cope with the demands of stress. Functionally, the Adrenal glands are closely linked to the Root Center, or chakra, which is the basic energy support and reservoir for the entire organism.
The basic temperament of the Adrenal glands is Hot or heating, to stimulate and energize several key physiological and metabolic functions, and to help the organism meet and adapt to the demands of stress. In this, the Adrenal glands are divided into two parts: a Medulla and a Cortex.
The Adrenal Medulla is Choleric and catabolic in its influence, and mobilizes the organism to meet the short term demands of acute stress through the adrenaline "fight, fright, flight" response. Blood sugar rises, heart rate increases, peripheral circulation increases, muscle tone and tension increases, as does mental alertness and stimulation.
The Adrenal Cortex is Sanguine and anabolic in its effects, enriching the blood with extra minerals and glucose to help the organism meet the energetic and nutritive demands of chronic, habitual or long term stress. The adrenocortical hormones, besides enriching the blood, also decrease swelling and inflammation; their anabolic action speeds healing and regeneration.
The Adrenal glands are strategically designed and placed by Nature's Creator to play an important and central role in stimulating and enhancing the functioning of all four faculties: Vital, Natural, Psychic and Generative.
For the Vital Faculty, the Adrenals lie right underneath the diaphragm, the breathing muscle and floor of the thoracic cavity on which the heart and lungs sit, to support and energize both these organs. The Adrenals enhance respiration and lung function and deepen inhalation; Adrenal insufficiency is often involved in many cases of chronic or congenital asthma or bronchitis. Adrenaline is a powerful stimulant to the heartbeat. And the adrenaline short term response to stress enhances and supports the Vital immune response.
For the Natural Faculty, the Adrenals sit right on top of each kidney, and enhance and support kidney function and urine metabolism and production; the kidneys are only as strong and resilient as the Adrenal glands that support them. Lying right behind the Pancreas, the Adrenal glands, through their hormones, support the Pancreas in regulating blood sugar levels, as we have seen.
For the Psychic Faculty, the Adrenals and the kidneys sit right astride the spinal column, which is the central conduit and nexus of the nervous system. Adrenaline stimulates mental alertness and enhances the functioning of the Sympathetic branch of the autonomic nervous system, which is adrenergic, or adrenaline dependent. The adrenocortical hormones favor the vegetative, anabolic functioning of the Parasympathetic branch of the autonomic nervous system. The health and balance of the Adrenals and the nervous system are closely linked.
For the Generative Faculty, particularly in the male, the Adrenal glands provide vital energetic support for male sexual function and response. The Adrenals also support healthy urinary function, which is closely linked with the sexual and reproductive functioning of the male reproductive system.
If you take good care of your Adrenal glands, they'll take good care of you. This is done mainly by stress reduction, and living a balanced, well-regulated lifestyle and mental/emotional life. If you don't take care of your Adrenal glands, various syndromes of imbalance or dysfunction could develop:
Adrenal exhaustion is the most common and generalized of these syndromes. It is usually caused by chronic or recurring flareups of Choleric anger and temper, extreme stress or shock, chronic exhaustion and fatigue, or irregular dietary and lifestyle habits that put your Adrenals on a wild roller coaster ride.
The chief signs and symptoms are extreme exhaustion and fatigue, moodiness and irritability, pain and/or weakness in the lower back, loins and knees, urinary debility, cold hands and feet, and impotence and declining virility in men. Sexual overindulgence can also exhaust the kidneys and Adrenals.
If chronic stress is unresolved, the Adrenal Cortex may compensate by producing too much cortisol, which has a Sanguine effect of pumping too much sugar and other nutrients into the blood. This is Cushing's syndrome, which is characterized by weight gain in the paunch, buttox and loins, glucose intolerance and rising blood sugar levels, elevated blood pressure, osteoporosis, possible kidney stones, menstrual irregularity in women, and chronic emotional stress and irritability. A moon face and buffalo hump on the back of the neck are also common. Many middle aged women, and men as well, with a weight problem, hypertension and/or type II diabetes are suffering from this syndrome.
Conversely, Addison's Disease is a nervous/aesthenic Melancholic condition caused by a deficient output of adrenocortical hormones. It's characterized by copious, dilute urine, with consequent fluid loss and dehydration. There can also be hypoglycemia caused by a hypersensitivity to insulin. There will be weakness, fatigue, dizziness, nausea, and diarrhea, as well as an intolerance for cold weather, and rheumatic and muscular aches and pains. Recovery from stress, injury and infection will also be compromised. The complexion tends to be dark and swarthy, with blackish freckles and blue-black discolorations around the nipples, mouth, rectum, scrotum in males, and vagina in females.
The gonads are the endocrine glands that produce the hormones responsible for the secondary sexual changes of puberty and adolescence, as well as the reproductive seed in both sexes. They also secrete hormones which, in conjunction with those of the pituitary, regulate the female reproductive cycle.
The gonads in men are the Testes, which secrete testosterone. The female gonads are the Ovaries, which secrete estrogen and progesterone. The gonads are functionally associated with the Generative Center, or chakra, called Gonades in Greek. The gonads are located near the Root Center at the base of the spine.
The full flowering of the Radical Moisture that takes place at puberty and adolescence in both sexes manifests secondary sexual changes in both men and women. Through procreation, the genes and seed of both parents, as well as the quintessence of their Radical Moisture, are passed on to the offspring.
The gonads are unique among endocrine glands in that they're not absolutely necessary for the day-to-day functioning of the organism, but are necessary only for procreation. And procreation isn't something that must continuously occur, but only at certain special times and reproductive phases of the overall life cycle. And so, the gonads remain dormant and undeveloped during childhood and youth, only to be awakened at puberty by hormonal signals from the Pituitary, the master gland of the endocrine system.
In spiritual and esoteric physiology, the Root and Generative centers are very closely linked, as are the Brow and Crown centers in the head and cranium. Physically, this linkage can be seen in the fact that the Adrenal glands produce small, supplementary amounts of the sexual hormones estrogen and testosterone.
The gonads and their functions will be covered in the following pages on the male and female reproductive systems, since they are the principal organs of the Generative faculty.