Hormones: the invisible messengers that govern our bodies

What exactly is the endocrine system and what does it do?

The endocrine system is a complex network of glands and organs that release hormones to control your body’s functioning. Hormones are like messengers for your body that control important functions like your sleep-wake cycle, growth and development, and homeostasis (i.e., state of balance). For example, when you are stressed, your adrenal glands release hormones like adrenaline, causing your heart to race and your blood pressure to spike– this is your body’s way of preparing for action in what’s known as the ‘‘flight or flight’’ response. Some other key hormone-secreting glands and organs that you may know include: 1) the thyroid, which plays an important role in your body’s metabolism, 2) the pancreas, which helps regulate blood-sugar levels, and 3) the ovaries, which secrete hormones involved in female sex characteristics and processes like menstruation and pregnancy.

How are women affected by hormonal changes?

Perimenopause and menopause

Many of us know about the role of estrogen in female sex characteristics, but it does more than that! Estrogen is also important for maintaining healthy, strong bones and managing cholesterol levels. As women reach perimenopause, estrogen levels fluctuate, leading to irregular menstrual cycles, hot flashes, difficulty sleeping, etc. After menopause, women are at an increased risk of developing heart disease and osteoporosis due to the drop in estrogen and its protective effects on the body.

Pregnancy

In contrast to menopause, pregnancy causes a dramatic increase in estrogen and progesterone to support the developing fetus. Several other hormones, such as human chorionic gonadotropin (HCG) are secreted by the placenta for this same purpose. Certain hormones are also involved in the suppression of the mother’s immune system during pregnancy to prevent fetal rejection.

What are the effects of hormone imbalances?

Hormonal imbalances can lead to all sorts of issues. The following list provides some insight into a few common ones.

Mood disorders

Some common types of mood disorders are postpartum depression, seasonal affective disorder, bipolar disorder and major depressive disorder (or simply, depression), being the most common. One of the main features that characterizes certain mood disorders like depression is the abnormal level and/or function of hormones like serotonin (mood regulation), norepinephrine (alertness, arousal and attention) and dopamine (motivation and reward behaviour). While these imbalances are a factor, genetic, psychological and environmental influences also play a role.

Polycystic Ovarian Syndrome (PCOS)

PCOS is a condition that affects 1 in 10 women of childbearing age. It is a result of an imbalance of the male hormone androgen, too much of which leads to irregular periods, excess facial and body hair, problems with fertility and development of cysts in the ovaries. Although the exact cause of PCOS is not known, certain symptoms like high insulin levels can also drive the condition. Insulin is a hormone that brings glucose into your cells and out of your bloodstream. If your cells become resistant to the action of insulin, this can lead to increased androgen production, which interferes with ovulation. Type 2 diabetes, infertility and obesity are some of the main complications of PCOS.

Thyroid disease

The thyroid gland plays a major role in your body’s metabolic functioning. Thyroid hormones help control our body temperature, heart rate, and protein synthesis. An underactive thyroid (hypothyroidism) can be caused by an auto-immune condition, radiation or infection. Symptoms include weight gain, fatigue, muscle weakness and sensitivity to cold. An overactive thyroid (hyperthyroidism) can also be caused by an auto-immune condition, infection or non-cancerous nodules. Symptoms include weight loss, anxiety, sensitivity to heat, and heart palpitations.

Diabetes

The pancreas releases insulin, which allows glucose from the blood into the cells to be stored and used for energy. If glucose cannot make its way into the cells, it stays in the blood, causing an increase in blood sugar levels, which can be very dangerous and lead to other health conditions, such as cardiovascular disease, diabetic neuropathy (nerve damage), nephropathy (kidney damage), etc. There are two main forms of diabetes: type 1 and type 2 diabetes. Type 1 diabetes is an autoimmune condition in which the cells of the pancreas are attacked by the body and can no longer produce insulin. This requires regular insulin injections to manage blood sugar levels. Type 2 diabetes is known as the preventable form of diabetes and can even be reversible with proper diet and exercise. Type 2 diabetes is more common in inactive adults with obesity.

Stress and the HPA axis

The hypothalamic-pituitary-adrenal (HPA) axis is your body’s main way of responding to stress. It consists of three hormone-releasing glands that act on one another to ultimately raise your body’s cortisol levels in response to a stressful situation. The human body is designed to respond to stress by making short-term physical and mental adjustments. The stress response helps keep us alert, motivated and ready to avoid danger. However, chronic stress and chronically elevated cortisol can damage our bodies. The HPA axis is meant to have a fine-tuned negative feedback loop, i.e., too much cortisol in your body will trigger it to stop making more. Experiencing frequent or intense stress and other issues can cause HPA axis dysfunction, which can increase your risk for other health conditions, like increased inflammation and immune system dysfunction, mental health conditions, high blood pressure and cardiovascular disease, etc. So, learning how to manage our stress levels is very important for our mental and physical health.

How does exercise affect hormones?

It is well understood that exercise has many positive benefits on the body. Apart from the obvious things like maintaining a healthy body weight, and increasing muscle strength and endurance, exercise also affects our hormone activity. Growth hormone, insulin, and endorphins are some examples of hormones that are influenced by exercise; their roles are summarized below.

Human growth hormone (HGH) and insulin-like growth factor-1 (IGF-1)

HGH is an anabolic hormone secreted by your pituitary gland regularly throughout the day and is important for promoting growth, especially in children. Once a child has stopped growing, HGH no longer increases height, but helps to maintain normal body structure and metabolism. Physical activity produces greater HGH concentrations which, in turn, improves physical fitness. Certain factors will determine how much HGH is released, such as age, gender (higher secretion in males vs females), body fat percentage (decreased secretion with increased body fat), and type of training. Strength training and bursts of high-intensity exercise result in higher HGH secretion, thus promoting more muscle growth. Much of the muscle protein-stimulating effects of exercise are due to insulin-like growth factor-1 (IGF-1), which is stimulated by HGH levels (higher or lower HGH levels results in higher or lower IGF-1 levels, respectively).

Endorphins

Endorphins are endogenous opioids produced by the brain that act as natural pain-relievers and trigger feelings of euphoria. There are many different types of endorphins in the body, but beta-endorphins are the most powerful. Exercise is one of the most effective ways to boost endorphin production, which in turn helps reduce the symptoms of depression, manage stress and anxiety, as well as improve confidence and self-esteem. Activities like swimming, dancing, and running can trigger the release of endorphins, leading to the “runner’s high”. Researchers found that adults who engaged in an hour of high-intensity interval training (HIIT) experienced a significant increase in endorphin release compared with those who engaged in an hour of less intense exercise. Higher endorphin levels also help boost dopamine release, which is a neurotransmitter involved in mood regulation and motivation. For example, after exercise, endorphins provide the ‘‘feel good’’ sensation, and dopamine provides the motivation to continue exercising.

Insulin

As mentioned above, insulin is a hormone involved in the storage of energy substrates from food into your tissues. Exercise increases insulin sensitivity, which means your body can better regulate blood sugar and store energy more efficiently. This increased sensitivity can last up to 48 hours after exercise. Repeated exercise training induces longer-lasting adaptations in several tissues that improve insulin action. This is why regular exercise is recommended for several insulin-resistance type conditions such as obesity and type 2 diabetes.

Brain plasticity

Engaging in physical activity can optimize the synthesis, metabolism, and release of hormones that improve mood decrease feelings of anxiety. Physical activity has also been known to improve stress by reducing resting cortisol levels and inflammation and improving sleep quality. Exercise can help reverse the effects of anxiety and depression since it has been shown to improve functional and structural brain plasticity and increase levels of BDNF (brain-derived neurotrophic factor). These processes are responsible for repairing the damaged brain circuits caused by mood disorders or injury. The American College of Sports Medicine (ACSM) recommends 150 minutes of aerobic activity per week at 40% to 60% intensity for overall health, although improvement in depressive symptoms have been observed after 20 min sessions 3 times per week.

In conclusion, hormones are very involved in our mental and physical health. They can be influenced by so many factors, but practicing healthy lifestyle habits is a good start to maintaining proper functioning of our body’s systems.

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