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Endocrinology and Fertility: The Endocrine System is Vital for Reproductive Health



Reviewed by Christine Traxler, MD

Endocrinology is the study of the endocrine system. The endocrine system is vital for fertility. We use the endocrine system as a reference point for maintaining healthy fertility a lot, but do most of us know what the endocrine system is or what it does for our body in relation to our fertility? For most of us, I would answer no. It is never really thought of unless we are taking a physiology and anatomy class, or until we are referred to a Reproductive Endocrinologist for our fertility struggles. I thought it would be helpful for you to learn what the endocrine system does and why it is so important for reproduction and overall health. This guide may also be helpful for those couples who are already seeing a Reproductive Endocrinologist.

The Endocrine System

The main function of the endocrine system is to serve as our body’s message center. The endocrine system is made up of endocrine glands. These glands secrete hormones into our blood or surrounding interstitial fluid. Interstitial fluid is the fluid that surrounds our cells. Hormones deliver messages and the endocrine system coordinates hormones. Hormones vary in their chemical structure, depending on the endocrine gland they are secreted from.

Our endocrine system works closely with our nervous system to maintain proper function. Most body organs are influenced by the nervous system and the endocrine system. The nervous system sends messages through nerve impulses, the endocrine system sends hormones as messages. For example, a muscle contracts in response to a neural impulse. The secretion of epinephrine (adrenalin) helps to make the contraction stronger and more forceful to help sustain it.

Without proper endocrine function, our bodies cannot maintain proper hormonal balance. The health of our endocrine system is essential to our ability to function properly. Our cells are genetically programmed to only receive and respond to messages from certain hormones. Hormone levels can be influenced by stress, fluid changes in the body, minerals in the blood and infection. Each endocrine gland plays a specific role in the ability of our body to maintain proper function. Each endocrine gland also communicates with the other in an amazing design. If one of the endocrine glands is not functioning properly, it may cause a broken link in communication with other endocrine glands or actions of the body, which may greatly impair fertility. Because the endocrine glands secrete hormones, and the hormones are messengers for actions within the body, if the gland is not functioning properly, hormonal imbalance occurs and the ability to reproduce may be impaired.

The Endocrine Glands

Hypothalamus
Located in the lower central part of the brain. This gland is the primary link between the nervous system and the endocrine system. Nerve cells within the hypothalamus secrete chemicals that stimulate or suppress hormone release from the pituitary gland. Hormones secreted by the hypothalamus are: Thyrotropin-releasing hormone (TRH) stimulates secretion of thyroid stimulating hormone (TSH). Corticotropin-releasing hormone stimulates secretion of adrenocorticotropic hormone (ACTH). Gonadotropin-releasing hormone (GnRH) stimulates the secretion of both follicle stimulating hormone (FSH) and luteinizing hormone (LH). Hypothalamic inhibitory hormones: Prolactin-inhibiting hormone (PIH) and somatostatin. Also included is another: growth hormone releasing-hormone (GHRH).

Pituitary Gland
This is considered the master gland. It is made up of two parts, the anterior and the posterior lobes. The anterior regulates the thyroid, adrenals, and reproductive glands. The posterior lobe releases antidiuretic hormone, this helps to maintain control of body water balance through its effect on the kidneys and urine output. The posterior lobe also releases oxytocin, which stimulates contractions of the uterus that occur during labor. For each positive feedback loop (communication through stimulation and secretion of certain hormones) there is also a negative feedback loop as well (inhibition), in order to maintain balance. I like to think of it as a thermostat. Here is a good example of how stimulation and inhibition in the endocrine system work…The hypothalamus is like you, a person who can control the thermostat in your home. The thermostat is the pituitary, and the heat is hormones released by other endocrine glands. As the heat rises (stimulation of endocrine glands and release of their hormones) it signals the thermostat (pituitary) to shut off. As the heat decreases, it signals the thermostat to run again. The control person (hypothalamus) sets the thermostat (pituitary) to a regulate the heat (endocrine glands releasing hormones).

The pituitary secretes the following hormones:

  • Adrenocorticotropic hormone (ACTH) is produced in response to stress, which stimulates the adrenals to secrete cortisol. Glucocorticoids inhibit ACTH.
  • Thyroid-stimulating hormone (TSH) stimulates production of thyroid hormones thyroxine (T4) and triiodothyronine (T3). Inhibited by T3 & T4.
  • Growth hormone (GH) is important for all tissues of the body. Stimulated by GHRH; inhibited by somatostatin.
  • FSH and LH are stimulated by GnRH; inhibited by sex steroids (sex hormones).
  • Prolactin stimulates milk production, it is inhibited by PIH.

Adrenal Glands
The adrenals are made up of two structures; the adrenal cortex is the outer layer, the medulla is the inner layer. The adrenal glands secrete steroid hormones called corticosteroids or corticoids for short. The adrenals secrete 3 groups of steroid hormones…

  • Mineralocorticoids, which regulate our sodium-potassium balance (Na+/K+) by acting on the kidneys. This regulates our salt and water balance within the body.
  • Glucocorticoids, regulate the metabolism of glucose and other organic molecules.
  • Sex steroids, androgens: DHEA (the precursor to estrogen), testosterone, androstenedione and some estrogen/progesterone. These supplement sex hormones secreted by the gonads (testis and ovaries).

The adrenals release these hormones in response to stress. Stress may arise from intense emotion, physical bodily injury or overexertion, or through environmental factors such as toxins.

Thyroid Gland
The purpose of the thyroid gland is to take iodine from foods we consume and convert it to thyroid hormones: thyroxine (T4) and triiodothyronine (T3). Thyroid cells are the only cells in the body which can absorb iodine. The thyroid combines iodine and the amino acid tyrosine to make T4 and T3. T4 and T3, once released into the blood stream, control our metabolism. The thyroid is also responsible for proper growth, development, and repair of the body. It is extremely important for the development of the central nervous system. The metabolism of every single cell in our body is dependent on thyroid hormones.

Parathyroid
Embedded into the thyroid gland are four tiny glands called the parathyroids. These four glands work together to release parathyroid hormone. Parathyroid hormone works with the thyroid to regulate the level of calcium in the blood with the help of calcitonin, which is produced in the thyroid.

Pancreas
The pancreas is very interesting. It is both an exocrine gland* and endocrine gland. Most of it is an exocrine gland, but scattered throughout the pancreas are clusters of cells called pancreatic islets. These clusters of cells secrete the hormone glucagon and insulin, which regulate blood glucose levels.

Pineal Gland
This small cone shaped gland is located in the brain. This gland secretes melatonin. This action is stimulated by suprachiasmatic nucleus (SCN) in the hypothalamus. Melatonin regulates our sleep-wake cycle. At night it is most active and secretion of melatonin is high. In the day, the retina in our eyes depress SCN, reducing the stimulation to the pineal gland, resulting in lowered melatonin levels.

Thymus
The thymus produces T cells, which are lymphocytes. T cells are involved in immunity. The T cells attack and destroy foreign invaders to our bodies. This is important for fighting of any type of virus. Sometimes the T cells attack our own cells, those T cells are destroyed in the Thymus. The thymus is most active and at its largest during the embryonic and adolescent stage of life. As a human matures, sex hormones activate the decrease in growth of the thymus and it atrophies. It still functions somewhat, but not nearly as much as through our developing years. The thymus may play a role in immune-related fertility issues.

Gonads Testes (male)
These are located in the male scrotum. The testes secrete steroid hormones known as androgens. The most well-known androgen is testosterone. These sex hormones in males are responsible for spermatogenesis (creation of sperm) and the development of secondary sexual characteristics (enlargement and function of the penis, facial and body hair, deepening of voice, etc.) At puberty, FSH is required along with androgens to create spermatogenesis. In adult males, spermatogenesis happens without FSH. The testes also secrete a very small amount of estradiol. Androgens are also responsible for growth of muscles and hemoglobin synthesis.

Ovaries (female)
The two main sex steroids secreted by the ovaries are estrogen and progesterone. Estrogen is essential for healthy bone formation, healthy gene expression, maintaining healthy cholesterol levels, and formation of secondary sexual characteristics in females (pubic hair, breasts, etc.), and is vital for a healthy menstrual cycle. Progesterone is needed for healthy libido, bone formation, and proper blood clotting. One of the main actions of progesterone is to help support a developing embryo. If pregnancy occurs, the production of progesterone from the corpus luteum continues for about 7 weeks (it is then produced by the placenta for the duration of the pregnancy).

Egg cells develop in follicles within the ovary. The pituitary gland begins releasing FSH at the beginning of the menstrual cycle, the release of FSH signals some of the follicles in the ovary to begin maturing. As the follicles begin maturing, they release and increase the hormone estrogen. The rising estrogen level signals the pituitary gland to curb release of FSH. The rising estrogen levels signal the pituitary gland to release Luteinizing Hormone (LH). LH signals the follicle to open and release the mature egg; this is ovulation. This is the ovulatory phase. Estrogen levels peak during this time, progesterone begins to increase. The closed follicle produces the corpus luteum. This phase is called the Luteal phase. The corpus luteum produces progesterone. Both estrogen and progesterone stimulate the uterine lining to thicken. Estrogen remains relatively high, though progesterone levels gradually increase in preparation for fertilization. If the egg is not fertilized, it gradually disintegrates, no longer producing progesterone. Estrogen declines. This stimulates the uterine lining to shed, starting a new menstrual cycle.

What is a Reproductive Endocrinologist?

A reproductive endocrinologist is an Ob-Gyn (obstetrics and gynecology) doctor with special training in hormonal function as it pertains to reproductive function and infertility, reproductive medicine, as well as surgical procedures for anatomical disorders that affect fertility.

Should I Consider Seeing a Reproductive Endocrinologist?
There are some general guidelines that may help you to know when to see a reproductive endocrinologist. You may or may not identify with any of these, and remember these are general guidelines. These guidelines are also used by your general family doctor or OB Gyn, who does not have extra training to be an RE, to identify a potential referral to an RE.

  • Have been trying to get pregnant unsuccessfully for over a year or more.
  • You have a history of recurrent miscarriage.
  • You have a history of infertility.
  • You are over 35 and have never been pregnant, or have been trying unsuccessfully after 35 years of age.
  • You or your partner have been diagnosed with a sexually transmitted infection.
  • You or your partner have a reproductive medical condition (PCOS, anatomical disorder, diagnosed hormonal imbalance, known problems with the reproductive organs, etc.)
  • Irregular or absent menstrual cycle, especially long-term.

There is a myriad of ways that an issue with any of the endocrine glands can affect fertility. If you suspect a problem with any of the endocrine glands in relation to your fertility struggles, talk to your doctor about seeing a reproductive endocrinologist!

Once you decide to see a reproductive endocrinologist, know that getting a diagnosis is the first step. Just because you are diagnosed with an issue, does not necessarily mean you need to take medications. There are many natural alternatives, so check into those first, after you talk to your doctor about your prognosis. Many issues with an endocrine gland can be healed by natural means, or through dietary changes alone.

Did You Know There are Toxins in our Environment That Disrupt the Endocrine System?

With the advancement of science and technology, we have come to learn that there are human-made chemical toxins in our environment, known as endocrine disruptors. Endocrine disruptors are also known as xenohormones. Xenohormones bind to our hormone receptor sites, producing a hormone-like affect. These xenohormones mimic our natural hormones, competing for receptor sites. This may cause long-term hormonal imbalance. These chemicals have the ability to interfere with the natural functions and development of our bodies. Xenohormones have the ability to bind to our hormone receptor sites, disrupting the function of the endocrine system. Not only can they mimic our natural hormones, but they can block other hormones from binding to receptor sites.

All xenohormones are endocrine disruptors. They can alter how natural hormones are produced, metabolized, and eliminated.

The most well-known of all endocrine disruptors are xenoestrogens, which mimic estrogen in the body. To learn more about this please read our Estrogen Fertility Guide…

Adaptogen Herbs for Protecting & Nourishing the Endocrine System

Adaptogen is one of the many definitions for the therapeutic action a plant has. Adaptogen herbs are nourishing to the entire endocrine system. Adaptogens increase resistance to mind-body stress, and enhance overall vitality and health. Plants recognized as adaptogens help to normalize the body’s functions even during diseased states, are non-toxic, nutritive, and have been deemed safe for long term use.

The following herbs and supplements may help to support proper endocrine function…
Adaptogen herbs that support endocrine system function:

  • Maca (Lepidium meyenii)
  • Ashwagandha (Withania somnifera)
  • Schizandra (Schisandra chinensis)
  • Fo-Ti, also known as He Shou Wu & Ho Shou Wu (Polygonum multiflorum)
  • Licorice (Glycyrrhiza spp.)
  • American ginseng (Panax quinquefolius)
  • Eleuthero, formerly known as Siberian Ginseng (Eleutherococcus senticosus)
  • Gotu Kola (Centella asiatica)

Other Important Supplements for Overall Endocrine Function

I hope you have learned a lot and now realize the importance of the endocrine system, for not only daily function of our entire bodies, but for our fertility as well!

*Exocrine glands are a type of ductal glands that secrete their products (including digestive enzymes and some hormone chemical messengers) into ducts that lead directly into the external environment. They are the counterparts to endocrine glands, which secrete their products (hormones) directly into the bloodstream (ductless glands) or release hormones (paracrines) that affect only target cells nearby the release site. Source: wikipedia.org/wiki/Exocrine_gland

References

About the Author

Dalene Barton - Certified Herbalist, Birth Doula

Practicing natural health and herbalism for over 18 years, Dalene received her training and herbal certification under the guidance of Lynn Albers at Yarmony Mt. Herbal College in Colorado in 2000. She went on to become a Certified Birth Doula at Birthingway College of Midwifery in Portland, Oregon in 2007. As a Birth Doula, Dalene has helped to bring many new lives in to this world. Dalene has written 280+ fertility articles and with her vast array of herbal and holistic healing knowledge has helped 1000's of women on their journey to Motherhood.

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