Optimal functioning of Vagus nerve is critical for overall health
Vagus nerve regulates many of the body functions by facilitating synthesis, release or action of various hormones in the body. Some of Vagus nerve effects on body hormones are
1 :: Vagus nerve normalizes the elevated hypothalamic-pitutary-adrenal (HPA) axis. HPA axis is comprised of hypothalamus (Brain), pituitary (Brain) and adrenal glands (present near kidneys) and is known as body’s central stress response system and regulates body processes like digestion, immune system, mood and emotions, libido and energy storage and expenditure.
During stress (emotional, physical, injury or illness) hypothalamus stimulates pituitary gland by releasing a hormone called corticotropin releasing hormone (CRH).
Upon stimulation, pituitary gland releases another hormone called adrenocorticotrophic hormone (ACTH), which is transported in circulation to adrenal glands present near kidneys.
Adrenal glands rapidly synthesize cortisol, epinephrine and norepinephrine (stress hormones) in response to pituitary stimulation.
These hormones initiates fight or flight response in the body.
Activation of HPA axis can induce physical changes in the body, including increased respiratory and heart rate, pain, elevated level of inflammatory mediators and suppression of immune system.
These changes are detected by Vagus nerve, which once stimulated, can inhibit HPA axis by bringing about neuroendocrine homeostasis in the body.
2 :: Vagus nerve boosts testosterone production. Low levels of testosterone can lead to moodiness, weight gain, loss of muscle mass and diminished libido.
What suppresses testosterone levels? Elevated level of stress hormone Cortisol affects the release of testosterone from testicles. Generally an enzyme called 11ßHSD-1, produced within the testicles, can protect testosterone from acute effects of stress.
But, this enzyme cannot neutralize elevated level of cortisol and due to this, freshly produced testosterone hormone gets damaged even before they are released from the testicles.
Vagus nerve stimulation helps check the elevated cortisol in the blood; boosts testosterone production to the required levels.
3 :: Estrogen dependent antinociceptive mechanism is mediated by Vagus nerve. It is reported that estrogen modulates visceral (body organs) pain. A study published in journal of pain 2014, described the exact mechanism how estrogen processes antinociceptive (reduction of visceral pain) effects and reported that the mechanism of pain reduction is carried by vagus nerve.
4 :: Vagus nerve regulates Growth Hormone (GH) secretion. What happens in suppressed Growth Hormone (GH)? Growth hormone (GH), also known as Somatotropin stimulates growth, cell reproduction, and cell regeneration and any imbalance can trigger reduced sex hormone-binding globulin (SHBG), reduced energy, muscle mass, strength, osteoporosis, impaired concentration, memory loss, baldness and cardiac dysfunction are some of the health concerns associated with Growth Hormone deficiency, in adults.
The growth hormone is secreted from pituitary gland in brain. Its secretion is dependent on hormones secreted by hypothalamus. Recently it is reported that grehlin, the hunger hormone secreted by gastrointestinal tract also induces growth hormone secretion.
The vagus nerve is crucial in the regulation of Growth Hormone (GH) secretion from pituitary gland and it also mediates ghrelin “hunger hormone” dependent growth hormone secretion (regulatory peptides 2011).
5 :: Vagus nerve controls hormonal regulation of appetite. Hormones, nutrients and neural influence control regulation of feeding behavior.
Hormones like Cholecystokinin (CCK) controls short-term inhibition of food intake and leptin controls long-term feeding behavior and body weight.
Both CCK and leptin generate satiety signal via vagus nerve. It is conceivable that malfunction of vagus nerve may result in eating disorders (Journal of Neurogastroenterology and Motility 2011).
6 :: Vagus nerve controls the Glucose lowering effect of insulin; glucose homeostasis. Insulin activates K-ATP channels in arcuate nucleus in the hypothalamus and modulates food intake, energy balance and glucose homeostasis.
Vagus nerve decreases release of agouti-related protein (AgRP), a potent appetite stimulator. Insulin signaling via Vagus nerve reduces glucose production from liver by decreasing enzymes required to produce glucose.
7 :: Vagus nerve stimulation releases vasoactive intestinal peptide (VIP). Vagus nerve stimulation increases level of VIP, which stimulates heart contractility. It also causes dilation of blood vessels in heart, lowers blood pressure, and relaxes muscles of stomach and gall bladder.