Endocrine functions and HPA...this has to do with stress?

The hypothalamic-pituitary-adrenocortical axis controls are one of the two major functioning systems that manage endocrine functions (Vedhara & Irwin, 2005). The endocrine system manages the release of hormones into a person’s circulatory system based upon activities that are signaled both during stressful situations as well as during times of relaxation on a cyclical basis.

The hypothalamus is located at the base of the brain and is connected to the pituitary gland (Vedhara & Irwin, 2005). Further, the hypothalamus acts in a way that it could almost be seen as the message coordinator, regarding hormone releasing functions, for the rest of the brain. When stimulated a variety of hormones are released into the blood stream such as CRH, TRH, GHRH, GnRH, ACTH, LH, TSH, and GH.

The pituitary gland is divided into two sections which are the anterior pituitary and the posterior pituitary sections. The anterior pituitary manages the neurons released from the hypothalamus, carried them down the pituitary stalk, and either increases or decreases the release of the anterior pituitary hormones (Pinel 2006). The posterior pituitary receives synthesized oxytocin and vasopressin from the hypothalamus and then releases it into the circulatory system. The pituitary gland receives hormones produces by nuclei in the hypothalamus and the pituitary stalk then transfers the hormones into the anterior pituitary lobe (Vedhara & Irwin, 2005). These hormones, once introduced into the blood stream, change the behavior of their target cells by binding to their surface and acting upon receptors that are located in the cells.

The HPA axis is stimulated by the release of adrenal glucocorticoids into the blood stream in an effort to prepare the person for the stressful event (be it real or perceived). Cortisol is one of the more impactful hormones released and managed by the HPA axis (Vedhara & Irwin, 2005). This secretion works on both an “as needed” distribution as well as a cyclical distribution during the mornings and the afternoons for most individuals.

Hypercortisol which can result in anxiety and depression may be an effect of over exposure to specific stressors, and as discussed in the General Adoption Theory by Selye, may lead to illness, depression, or death so therefore it is best to not allow for stressful situations to go unmanaged (Edwards, 2000 & Lovallo, 2004). Further, there are interesting side effects to a variety of hormonal supplements with regard to the over activity of the HPA axis. For example, it has been cited that women who received supplements of oestragen during menopausal time experience suppression in HPA axis when they are exposed to both intentional and unintentional stressors (Dayas, 2000).

Dayas, C. V. (2000). Effects of chronic oestrogen replacement on stress-induced activation of hypothalamic-pituitary-adrenal axis control pathways. Journal Of Neuroendocrinology, 12(8), 784-94.

Edwards, C. (2000). That psychiatrist on the couch isn’t crazy – Interview. Insight on the News. Retrieved September 13, 2007 from Find Articles database: http://findarticles.com/p/articles/mi_m1571/is_30_16/

Lovallo, W. (2004). Stress & Health: Biological and Psychological Interactions. Thousand Oaks, CA: Sage Publications.

Pinel, John P. J. (2006). Biopsychology with “beyond the brain and behavior” (6th ed.). Boston: Allyn and Bacon.

Vedhara, K., & Irwin, M.R. (2005). Human Psychoneuroimmunology. New York, NY: Oxford University Press.

Comments

[Susan Pease Banitt, LCSW]

Great article!