There are scientific studies being done on the effects of yoga on the endocrine system – the hormones. This is very promising work. For a long time, people have tried to tie yoga nadis to the nervous system, and it is certain that some parallels can be drawn between nerve plexi and the chakras. But this will never give the whole picture of just why a sustained hatha yoga practice, over years, brings about such overall good health and humour.
The Endocrine System
The endocrine system is composed of glands, organs and the substances they produce, known as hormones. Hormones are secreted or excreted in miniscule quantities, but they have far-reaching effects. Any woman who has ever taken hormonal birth control or even had a period knows this.
Of great interest to those working with breast cancer is the so-called HPA axis, or Hypothalamo-Pituitary-Adrenal axis. This is basically a cascade within the endocrine system in which one gland signals another. The HPA helps control our reactions to stress, among other things. The hypothalamus and the pituitary glands are nestled beside each other, and the link between the nervous system and the endocrine system is right here. Basically, the hypothalamus secretes hormones that cause the pituitary to secrete hormones. The hypothalamus receives information from the brain stem, that is, information from our body. The anterior pituitary gland is where the hormones are secreted, and has been found to be activated by GABA. Pituitary hormones then signal the adrenal glands, where cortisol is produced.
There is yet another hormone axis called the HPG axis, or Hypothalamo-Pituitary-Gonad axis. This axis signals and controls the sex organs. The majority of breast cancer patients are menopausal or peri-menopausal at diagnosis, and those who are still menstruating have their periods suppressed in a bid to reduce oestrogen production. The crux of the matter is the the Hypothalamus signals the Pituitary and this released two hormones, LH and FSH. FSH does the final conversion of androgen to oestrogen, but LH helps produce the androgen, which coverts to oestrogen. This process uses an enzyme called aromatase, and you may have heard of aromatase inhibitors, a class of drugs used in breast cancer patients with hormone-sensitive tumours.
One of the hormones that is of interest to yoga practitioners is cortisol. Cortisol is produced in the adrenal glands and secreted into the blood. Almost all cells of the body have cortisol receptors (these are like antenna or tunnels on the cell walls and they all the cells to transport the cortisol into the cell, where it can exert its effect.) So, if you have high cortisol levels, you may see a wide range of effects in the body, including:
What is cortisol? In it’s normal function, cortisol helps us meet life’s challenges by converting proteins into energy, releasing glycogen and counteracting inflammation. For a short time, that’s okay. But at sustained high levels, cortisol gradually tears your body down. Cortisol is one essential we can’t live without. But too much of a good thing is not healthy.
Sustained high cortisol levels destroy healthy muscle and bone, slow down healing and normal cell regeneration, co-opt biochemicals needed to make other vital hormones, impair digestion, metabolism and mental function, interfere with healthy endocrine function; and weaken your immune system.
Adrenal fatigue may be a factor in many related conditions, including fibromyalgia, hypothyroidism, chronic fatigue syndrome, arthritis, premature menopause and others. It may also produce a host of other unpleasant symptoms, from acne to hair loss.
Here is a summary of the scientific studies substantiating the fact that the practice of Hatha Yoga reduces blood cortisol levels.
Another hormone of interest to yoga practitioners is GABA (Gamma-amino butyric acid). Low GABA levels in the brain are linked to anxiety and depression. Anyone who has had cancer treatment knows that depression is rarely far away. In my opinion, it is a very natural reaction to the physical trauma of treatment and the emotional trauma of facing your own mortality. But depression cannot be allowed to continue unchecked, and the practice of Hatha Yoga helps regulate mood. For example:
In a German study published in 2005, 24 women who described themselves as “emotionally distressed” took two 90-minute yoga classes a week for three months. Women in a control group maintained their normal activities and were asked not to begin an exercise or stress-reduction program during the study period.
Though not formally diagnosed with depression, all participants had experienced emotional distress for at least half of the previous 90 days. They were also one standard deviation above the population norm in scores for perceived stress (measured by the Cohen Perceived Stress Scale), anxiety (measured using the Spielberger State-Trait Anxiety Inventory), and depression (scored with the Profile of Mood States and the Center for Epidemiological Studies Depression Scale, or CES-D).
At the end of three months, women in the yoga group reported improvements in perceived stress, depression, anxiety, energy, fatigue, and well-being. Depression scores improved by 50%, anxiety scores by 30%, and overall well-being scores by 65%. Initial complaints of headaches, back pain, and poor sleep quality also resolved much more often in the yoga group than in the control group.
I really could write all day, but my daughter will get mad at me, and Sunday is Sunday. I will leave you to think about this:
Hatha yoga reduces blood cortisol, stimulates the vagus nerve and just darn well calms us down. The brain stem recognises our altered physical state and sends this information to the Hypothalamus. The Hypothalamus says to the Pituitary “all is good, settle down”. The HPG and HPA axes find homeostasis and we establish a feedback loop of calm and settledness. To any scientists reading this, I know it sounds facile. But I think that your research – and our practice- will lead us to this conclusion.
In the meantime, keep practising. We find peace in the poses. Om.
For your reading pleasure, a few curated links to articles discussing Yoga and the endocrine system.