Hormone Replacement Therapy (HRT) - Endocrine System

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Hormone Replacement Therapy (HRT) & the Role of the Endocrine System

How HRT can Benefit Me:
Hormone Replacement Therapy (HRT)
is a medical treatment usually given to women to replace and help balance declining estrogen and progesterone levels during or near menopause. There are also many other reasons why a Doctor or other qualified Medical Practitioner might prescribe supplementary sex hormones.

HRT can help relieve:

  • Sweating
  • Hot flashes
  • Night sweats
  • Vaginal dryness
  • Bone loss
  • Mood changes
  • and other symptoms of menopause. (Medical News Today and Medicinenet)

The Endocrine System plays a vital role in Respiration, Metabolism, Growth and Development, Sexual Function and Reproduction, Heart Rate and Blood Pressure, Appetite, Sleeping and Waking Cycles, Body Temperature, and Movement.

Hormones are produced by glands and sent into the bloodstream to the various tissues in the body. They send signals to those tissues to tell them what they are supposed to do. When the glands do not produce the right amount of hormones, diseases develop that can affect many aspects of life. (Hormone.org)
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Bioidentical Hormone Replacement Therapy (BHRT) and Hormone Replacement Therapy (HRT) are BIG topics…What you see in this section is really just a starting point of the discussion.

Hormone Therapy has been a controversial topic since the various forms of estrogen were discovered in 1929 at the St. Louis University Medical School by scientist Edward Adelbert Doisy. When estrogen, in the form of Premarin, was approved by the FDA in 1942 it became widely available as a treatment for menopausal hot flashes. This was two decades before the first hormonal birth control pill was approved in 1960. (Everyday Health)

A landmark 2002 US study, The Women’s Health Initiative (WHI) was a long-term national health study comparing estrogen plus progestin with placebo as a primary strategy for preventing heart disease, breast and colorectal cancer, and osteoporosis in menopausal women (aged 50-79, with an average age of 65). The study was stopped after only 5.6 years because results were interpreted to indicate that the risks outweighed the benefits. The media attention surrounding the publication of the initial results of WHI led to much fear and confusion  for some time, regarding the use of Hormonal Therapy (HT) after menopause. 

Subsequent studies from the WHI and other organizations clearly showed that younger women and those close to menopause had a very beneficial risk-to-benefit ratio. The results showed similar protective effects for coronary disease and a reduction in mortality that had been shown in earlier observational studies, which had also focused on younger symptomatic women. 

Although ongoing study continues in this important arena, it seems that there is even some acceptance in the mainstream medical community for using HRT to treat some women with symptoms at the onset of menopause. (The Journal of Clinical endocrinology & Metabolism).


The Endocrine System is made up of glands that produce and secrete hormones, chemical substances produced in the body that regulate the activity of cells or organs. These hormones regulate the body’s growth, metabolism (the physical and chemical processes of the body), and sexual development and function.

The hormones are released into the bloodstream and may affect one or several organs throughout the body. Hormones are chemical messengers created by the body and they transfer information from one set of cells to another to coordinate the functions of different parts of the body.

The major glands of the endocrine system are the hypothalamus, pituitary, thyroid, parathyroids, adrenals, pineal body, and the reproductive organs (ovaries and testes). The pancreas is also a part of this system; it has a role in hormone production as well as in digestion.

The endocrine system is regulated by feedback in much the same way that a thermostat regulates the temperature in a room. (eMedicine Health)

In a publication in the Journal of Obstetrics and Gynaecology Canada (JOGC) 2021 October 01 entitled, Guideline No. 422a: Menopause: Vasomotor Symptoms, Prescription Therapeutic Agents, Complementary and Alternative Medicine, Nutrition, and Lifestyle, the publishers’ objective was to provide strategies for improving the care of perimenopausal and postmenopausal women, based on the most recent published evidence. Their summarized findings are as follows:

  1. The vast majority of women in mid-life experience menopausal symptoms, the hallmark being vasomotor symptoms. A significant portion of these women have severe symptoms that greatly affect their quality of life (high correlation).
  2. For the management of vasomotor symptoms, menopausal Hormone Therapy is the most effective option and can be safely initiated in women without contraindications who are younger than 60 years of age or less than 10 years post-menopause (high correlation).
  3. Options for menopausal Hormone Therapy for vasomotor symptoms in women with a uterus include estrogen-progestogen therapy, a tissue-selective estrogen complex, or tibolone. Estrogen alone can be used in women who have had a hysterectomy (high correlation).
  4. The safety and efficacy of compounded Bioidentical Hormone Therapy have not been assessed with the same rigour as those of menopausal hormone therapy products approved by Health Canada (moderate correlation).
  5. Non-hormonal prescription therapies, including certain antidepressant agents, gabapentinoids, clonidine, and oxybutynin, may offer some relief from hot flashes but have their own adverse effects (moderate correlation).
  6. There is emerging evidence that Cognitive Behavioural Therapy may have positive effects on vasomotor symptoms (high correlation).
  7. There is insufficient evidence to support the effectiveness of any one natural health product for the management of moderate to severe hot flashes (low correlation).
  8. A healthy diet during menopause can reduce the risk of future chronic conditions, aid in weight management, and improve energy levels (high correlation).


    1. Healthcare Providers should offer menopausal Hormone Therapy as the most effective option for managing vasomotor symptoms (strong, high correlation).
    2. Menopausal Hormone Therapy can be safely initiated in women without contraindications who are younger than 60 years of age or less than 10 years post-menopause (strong, high correlation).
    3. Menopausal Hormone Therapy should be individualized after careful consideration of symptoms, medical conditions, health risks, family history, treatment goals, patient preferences, and timing of last menstrual period (strong, high correlation).
    4. Duration of menopausal hormone therapy should be individualized to the patient, based on ongoing symptoms, benefits, and personal risks. Periodic re-evaluation of menopausal Hormone Therapy is recommended (strong, high correlation).
    5. Women who have experienced loss of ovarian function or with decreased ovarian function before the age of 45 years should consider replacement hormone therapy until the average age of menopause (strong, high correlation).
    6. Estrogen-progestogen regimens can be continuous (i.e., estrogen-progestogen taken every day) or follow a cyclic regimen, with estrogen taken every day and progestogen taken for 12–14 days every month. In women with hysterectomy, estrogen alone can be taken every day (strong, high correlation).
    7. Options for perimenopausal women include progestogen alone, low-dose combined hormonal contraceptives, menopausal Hormone Therapy, or estrogen in combination with a levonorgestrel-releasing intrauterine system. (strong, moderate correlation)
    8. Non-hormonal prescription therapies can be considered when Hormone Therapy is contraindicated or not desired (strong, moderate correlation).
    9. For cultural traditional therapies, women should be offered the opportunity to work with a cultural leader; health care providers can discuss this option in partnership with women, in order to ensure cultural humility and cultural safety (strong, moderate correlation). (JOGC)


    The Endocrine System uses hormones to control and coordinate your body’s internal metabolism (or homeostasis), energy level, reproduction, growth and development, and response to injury, stress, and environmental factors. Following is a list of the primary human glands, the hormones they secrete, and their role in the workings of the Endocrine System:

    • Adrenal glands secrete aldosterone which regulates salt, water balance, and blood pressure.
      Adrenal glands also secrete corticosteroids which control key functions in the body; act as an anti-inflammatory; maintain blood sugar levels, blood pressure, and muscle strength; and regulate salt and water balance
    • The Pituitary gland secretes the antidiuretic hormone (vasopressin) which affects water retention in the kidneys and controls blood pressure.
      The Pituitary gland also secretes the adrenocorticotrophic hormone (ACTH) which controls the production of sex hormones (estrogen in women and testosterone in men) and the production of eggs in women and sperm in men.
      The Pituitary gland also secretes the growth hormone (GH) which affects growth and development, stimulates protein production, and affects fat distribution.
      The Pituitary gland also secretes luteinizing hormones (LH) and follicle-stimulating hormones (FSH) which control the production of sex hormones (estrogen in women and testosterone in men) and the production of eggs in women and sperm in men.
      The Pituitary gland also secretes oxytocin which stimulates the contraction of the uterus and milk ducts in the breast. [It is also sometimes referred to as the ‘love hormone’ because levels of oxytocin increase during hugging and orgasm.]
      The Pituitary gland also secretes prolactin which initiates and maintains milk production in breasts and impacts sex hormone levels.
      The Pituitary gland also secretes the thyroid-stimulating hormone (TSH) which stimulates the production and secretion of thyroid hormones.
    • The Kidneys secrete renin and angiotensin which control blood pressure, both directly and also by regulating aldosterone production from the adrenal glands.
      The Kidneys also secrete erythropoietin which affects red blood cell (RBC) production.
    • The Pancreas secretes glucagon which raises blood sugar levels.
      The Pancreas also secretes insulin which lowers blood sugar levels and stimulates the metabolism of glucose, protein, and fat.
    • The Ovaries secrete estrogen which affects the development of female sexual characteristics and reproductive development important for the functioning of the uterus and breasts. It also protects bone health.
      The Ovaries also secrete progesterone which stimulates the lining of the uterus for fertilization and prepares the breasts for milk production.
    • The Parathyroid glands secrete the parathyroid hormone (PTH) which is the most important regulator of blood calcium levels.
    • The Thyroid gland secretes the thyroid hormone which controls metabolism. It also affects growth, maturation, nervous system activity, and metabolism.
    • The Adrenal glands secrete epinephrine which increases heart rate, oxygen intake, and blood flow.
      The Adrenal glands also secrete norepinephrine which maintains blood pressure.
    • The Testes (testicles) secrete testosterone which develops and maintains male sexual characteristics and maturation.
    • The Pineal gland secretes melatonin which is released during night hours to help with sleep.
    • The Hypothalamus secretes the ‘growth hormone releasing hormone’ (GHRH) which regulates growth hormone release in the pituitary gland.
      The Hypothalamus also secretes the thyrotropin releasing hormone (TRH) which regulates thyroid stimulating hormone release in the pituitary gland.
      The Hypothalamus also secretes  the gonadotropin releasing hormone (GnRH) which regulates LH/FSH production in the pituitary gland.
      The Hypothalamus also secretes the corticotropin releasing hormone (CRH) which regulates adrenocorticotropin release in the pituitary gland.
    • The Thymus secretes humoral factors which help develop the lymphoid system. (Johns Hopkins Medicine)

    At the heart of the Hormone Therapy debate is the 2002 Women’s Health Initiative (WHI) study that concluded that the overall health risks exceeded the benefits from combined use of estrogen and progestin among healthy postmenopausal women.

    Experts say that the study had some caveats and the results are often misinterpreted.

    Dr. Wen Shen, an assistant professor of gynecology and obstetrics at Johns Hopkins Medicine in Maryland, says, “A lot of people, yes, are still going on the misinformation that was presented by the WHI. The amazing thing was that the trial was stopped and was evaluated and scrutinized, so we’re talking about 20 years ago. People are still misunderstanding it.”

    The study examined the effects of the combination of estrogen and progestin as well as estrogen alone in postmenopausal women. The average age of the women in that trial was 65, Shen said, while the average age of women going through menopause is 51.

    “When you hit 60, a lot of physiologic changes occur that makes it bad medically for you to start on Hormone Therapy and especially the only Hormone Therapy that they used in that trial, which was the oral conjugated equine estrogen (CEE) and medroxyprogesterone acetate (MPA)…There’s a lot of data that has come out now that shows women who start on Hormone Therapy very close to their menopause or even during their perimenopause, before they become postmenopausal, actually are healthier and have greater longevity and that is attributed to the beneficial effects of estrogen on heart health, bone health, and brain health, in early stages of menopause,” Shen said.

    Education is key to understanding the risks associated with hormone therapy.

    “…Not all estrogens and progesterones are created equal,” Shen said. “There are different side effects and different benefits to the types of estrogens, and…the estrogen patch is overall much safer and lower in the risks that were found from the WHI.”

    Women can make smart decisions for themselves when they’re “fully apprised of the different pros and cons, instead of harboring misinformation and fears that are unfounded.”

    Dr. Julian Schink, Chief of Gynecologic Oncology for the Cancer Treatment Centers of America in Illinois, acknowledges that there are critiques of the WHI study, like the average age of the women in the trial. 

    There are women for whom hormones aren’t an option. “Anybody who’s had estrogen sensitive cancer, which is typically a breast cancer, should not be taking hormones,” he said. “There are some clotting disorders that are exacerbated by estrogen,” he added. “So people who’ve had known blood clotting disorders should avoid estrogens.”


    The Endocrine System is made up of a complex network of glands, which are organs that secrete substances. The glands of the Endocrine System are where hormones are produced, stored, and released. Each gland produces one or more hormones, which go on to target specific organs and tissues in the body.

    The glands of the endocrine system include:

    • Hypothalamus. While some people don’t consider it a gland, the hypothalamus produces multiple hormones that control the pituitary gland. It’s also involved in regulating many functions, including sleep-wake cycles, body temperature, and appetite. It can also regulate the function of other endocrine glands.
    • Pituitary. The pituitary gland is located below the hypothalamus. The hormones it produces affect growth and reproduction. They can also control the function of other endocrine glands.
    • Pineal. This gland is found in the middle of your brain. It’s important for your sleep-wake cycles.
    • Thyroid. The thyroid gland is located in the front part of your neck. It’s very important for metabolism.
    • Parathyroid. Also located in the front of your neck, the parathyroid gland is important for maintaining control of calcium levels in your bones and blood.
    • Thymus. Located in the upper torso, the thymus is active until puberty and produces hormones important for the development of a type of white blood cell called a T cell.
    • Adrenal. One adrenal gland can be found on top of each kidney. These glands produce hormones important for regulating functions such as blood pressure, heart rate, and stress response.
    • Pancreas. The pancreas is located in your abdomen behind your stomach. Its endocrine function involves controlling blood sugar levels.

    Some endocrine glands also have non-endocrine functions. For example, the ovaries and testes produce hormones, but they also have the non-endocrine function of producing eggs and sperm, respectively.

    Explore the Research

    We believe you should have access to high-quality research to help you make informed health decisions. Below are four trusted databases you can use as tools to expand your healthcare knowledge.