Given the types of lifestyles American live, the concept of stress has pervaded our social and biological view of being human. But while we are often told of stressful events (loss of family member, divorce, major life changes), what actually defines stress from a physiological perspective has been more difficult to grasp. Some have said that nearly 75% of the diseases prevalent in western society today are somehow related to the stress mechanisms of the body. Our topic is narrower here, we hope to show how stress (emotional or physical) affects the adrenal gland and how to test and support the stressed adrenal gland in a gentle but profound way.
Stress- What is it?
While it may seem obvious to most of the readers, the definition of “stress” has not been easily agreed upon by biologist over the past
75 years. Does it define the necessary changes in adapting to a stressor, or the malfunction of not adapting to these same stressors? When we
think of stress, we often think of negative stress, or as some would say “distress”; but positive events (wonderful surprises, passion, athletic
competition) can elicit seemingly identical responses, from a physiological perspective.
The scientist who, more than anyone, brought the concept of stress to the forefront is Hans Selye. His book The Stress of Life (26), written
for the lay audience, popularized the notion of stress as the general response to a wide variety of insults. His research, mostly with rats, revealed
a recurring set of physiological outcomes (hypertrophy of the adrenal gland, atrophy of the lymphatic organs, and ulcers in the stomach)
when these rats were exposed to a variety of insults. He later formed what he called the general adaption syndrome (G.A.S.) in a three-stage
1. The alarm reaction, involving increased adrenocortical secretion and activation of the sympathoadrenal system.
2. The stage of resistance, involving the balancing of the adrenocortical hormones’ affect on water and electrolyte balance and
carbohydrate metabolism. The “true adaption” to stress.
3. The stage of exhaustion, involving the depletion or exhaustion of the adrenal glands’ ability to make corticosteroids.
We recognize that Selye has simplified a very complex set of responses and his model is, at times, very limited. Some have pointed out
that most of the limitations with the G.A.S., as defined, is that the animals under stress were unable to do anything to remove themselves
from the stress (27). As such, this model may be best used for measuring chronic, unavoidable stressors (internal inflammations, unavoidable
job stresses). Even with some of these limitations, it does give us a framework to measure stress, especially as it pertains to the hypothalamuspituitary-
adrenal axis (HPA axis) and the consequences on human health. Let us first look at the adrenal gland and the HPA axis controlling
The Adrenal Gland:
The adrenal glands are small (5 grams) glandular tissues lying atop each of the kidneys (See figure 1). Originally called suprarenal glands,
because of their location, they were first discovered by the anatomist Bartolomaeus Eustachius, further described by Cuvier and then later by
Thomas Addison. The inner portion, called the medulla, secretes epinephrine and norepinephrine and is an extension of the sympathetic
nervous system. The larger outer portion, called the cortex, is responsible for secreting various steroid hormones. From every point of view,
functional, structural, and developmental, the adrenal cortex and medulla can be considered as two separate glands. We will consider only
the cortex in this particular paper.
Of the nearly 30 steroid hormones produced by the adrenal cortex, the principal ones include aldosterone (a mineralocorticoid), cortisol
(a glucocorticoid), and various sex hormones and their precursors (DHEA, androstenedione). The mineralocorticoids play an essential role
in regulating potassium and sodium levels and water balance. DHEA and its metabolites have diverse effects during the lifecycle of the
individual (see side panel for DHEA discussion). Our focus here is the glucocorticoid cortisol and its easily measurable stress response.