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It is commonly said in yoga classes that certain poses affect certain glands, the most common being that Shoulder Stand (Sarvangasana) stimulates the thyroid gland. This connection between Shoulder Stand and the thyroid has been repeated so many times that many consider it fact, which constitutes a form of cognitive bias known as availability cascade, wherein a collective belief gains more and more acceptance simply through its increasing repetition in public discourse. However, the claim of Shoulder Stand stimulating the thyroid gland has not been investigated scientifically and is based purely on speculation (Pierce 2011). While some studies have been conducted on thyroid conditions and yoga in general, we authors cannot find any studies in the scientific literature looking specifically at how Shoulder Stand might affect the thyroid gland. Furthermore, the idea that this pose might stimulate the thyroid gland does not make a lot of sense physiologically.
The workings of the endocrine system are much more complex than is suggested with this idea of applying manual pressure to create change. The endocrine system works through molecular and cellular processes in which one molecule initiates a cascade of events to create the desired outcome. The pituitary gland is the master that governs all other glands, and the pituitary is governed by the hypothalamus in the brain. The hypothalamus releases thyrotropin-releasing hormone, which is received by the pituitary, which then releases thyroid-stimulating hormone, which is then received by the thyroid to produce thyroid hormones. If the hypothalamus’ ability to produce thyrotropin-releasing hormone were impaired or the pituitary’s ability to produce thyroid-stimulating hormone were impaired, as might be the case if a tumor were present, the thyroid would not be able to produce the needed thyroid hormones no matter how many Shoulder Stands were performed. Similarly, if one’s diet were deficient in iodine, one’s thyroid would not be able to produce enough thyroid hormones, no matter what asanas were performed.
The reality is that there is no scientific evidence to support the notion that Shoulder Stand might directly affect thyroid function. Furthermore, does the thyroid need stimulating? Wouldn’t that depend on whether someone has an underactive versus overactive thyroid? On the other hand, just because there is no scientific evidence to support a claim does not mean that the claim is false. What we do know is that all moderate exercise will have some positive effect on the endocrine system, including the thyroid. General exercise has near-miraculous health benefits, even though it does involve applying pressure to the thyroid. We also know that elevated cortisol negatively impacts the thyroid, so taking time to relax, as we do in yoga, also benefits thyroid function. Simply moving and balancing that movement with relaxation are the best things we can do for overall health and among the best gifts we can offer to others.