Endocrine System
Excerpt from 70 Glorious Years of Yogacharya BKS Iyengar - Commemorative volume.
Sarvangāsana, or shoulder stand, which is the queen of āsana, also benefits the endocrine glands situated in the head and neck, especially the thyroid and the parathyroid glands. As the neck is flexed, greater blood flow is directed to the region of the neck. Moreover, the glands are compressed and massaged, thus stimulating them and removing the toxic elements.
The other inverted āsanas such as Viparita Karani would also act in a similar manner though to a lesser extent. In the erect position, these glands tend to have a lesser blood supply and the various organs of the abdomen tend to sag, reducing their function. The inverted āsanas also help other organs such as the stomach, spleen, liver and the kidneys to fall back into their normal positions due to the anti-gravity effect of these āsanas, allowing them to resume their optimal activity.
Matsyāsana and Uṣṭrāsana which are neck opening āsanas, stimulate and massage the thyroid and parathyroid glands.
Āsanas which open the thorax and the lungs include the backward bending āsanas such as Bhujangāsana, Urdhva Dhanurāsana, Śalabhāsana and Dhanurāsana. They improve the function of the lungs, and the oxygenation of the blood, so that the organs and glands receive a richer, oxygenated blood flow that improves their overall function.
The Supranrenals and the Islets of Langanerthans of the pancreas can be stimulated to produce more hormones by the forward bending āsanas such as Janu Sirsāsana, Paschimottanāsana, Halāsana and Uttanāsana. They increase the inter-abdominal pressure and massage the abdominal organs and glands releasing more hormones into the blood. Moreover, neural plexuses such as the coeliac and solar plexuses are also brought into alignment.
Āsanas such as Padmāsana, Virāsana, Gomukhāsana and Siddhāsana all increase the blood flow to the pelvic organs as well as compress and massage them, thus improving the function of the sex and the adrenal glands.
Āsanas such as Padahastāsana, Uttanāsana and Adho Mukha Svanāsana, which combine the effects of an inverted pose with those of a forward-bending pose, are powerful means of toning up the whole body, as all the endocrine glands are stimulated. Thus they are the best tonics for the body, and would be helpful in cases of debility, weakness, poor growth, neurasthenia and diabetes.
Prānāyāma, or breath control, are made up of techniques to improve one's control over various parts of our breathing process such as inhalation, exhalation and the pauses between them. However, these techniques are like a surgeon's knife. If used properly and by a skilled surgeon, it can remove any disease, but if used by an unskilled and inexperienced surgeon, who has not had the proper training under a senior experienced surgeon, it can cut through vital structures of the person and be harmful to him. Similarly, Prānāyāma is a very powerful tool, which if used carefully, can remove any disease and give supreme vitality to the body, and lasting peace to the mind. Prānāyāmas effects on the body are far-reaching.
By increasing the capacity of the lungs and the oxygenation of the blood, it reaches right down to the cellular level, improving the function of each and every cell, of each and every system of the body.
It eliminates all the toxic elements from the tissues, systems and glands and stimulates them to function at an optimal level.
Regulating the lungs is the most vital process in the cleansing of the human system.
Thus both āsana and prānāyāma have a tremendous beneficial effect on the endocrine system and if done regularly with faith and sincerity, can definitely improve a person's general health, and remove whatever illnesses he may be suffering from.
Extract from an article by Dr. J. T. Shah