9.1 Anatomy of the Neuroendocrine System

Post-traumatic neuroendocrine disorders involving the pituitary gland can be divided into posterior or anterior pituitary dysfunction depending on which anatomical area is involved.

9.1.1 Anatomy of the Pituitary Gland

The pituitary gland consists of two lobes derived from 2 different embryological pouches.

  • Anterior lobe (or adenohypophysis)
  • Posterior lobe (or neurohypophysis)

The pituitary gland is connected to the hypothalamus through the pituitary stalk and controls both homeostasis and endocrine function.

The anterior lobe contains glandular cells which secrete hormones into circulation. It is controlled by the hypothalamus through the vascular portal system. The posterior lobe contains the axons and nerve terminals of neurons which have their cell bodies in the hypothalamus.

The anterior lobe is responsible for the production of six important hormones which are secreted into the circulatory system 25. The six hormones produced include:

  • Adrenocorticotropic hormone (ACTH)
  •  Growth hormone (GH)
  • Thyroid stimulating hormone (TSH)
  • Luteinizing hormone (LH)
  • Follicle stimulating hormone (FSH)
  • Prolactin

These hormones serve to regulate endocrine systems in other areas of the body and are under control of hypothalamic releasing factors.

Hypothalamic releasing factors correspond with the hormones released by the anterior pituitary and include:

  • Growth hormone releasing hormone àgrowth hormone release
  • Somatostatin àdecreases release of growth hormone
  • Thyrotropic releasing hormone àthyroid hormone release
  • LHRH/GnRH àFSH and LH release
  • Corticotropic releasing hormone àACTH release
  • Prolactin releasing factor (PRF) and throtropin-releasing hormone (TRH) àprolactin

 

The posterior lobe is responsible for the secretion and storage of 2 hormones:

  • Vasopressin (or antidiuretic hormone (ADH)) promotes water retention in the kidneys, which allows for concentration of urine.
  • Oxytocin allows for milk let down in the breast and causes uterine contractions during labour.

 

9.1.2 Hormones Involved with the Neuroendocrine System

Following an ABI/TBI changes may be noted in hormones released by the pituitary gland26. Hormones released include: 

 

Table 9.1 Hormones Produced and Released by the Pituitary Gland

Glands

Hormones

 

Anterior pituitary

 

  • ACTH (AdrenoCorticotropic Hormone or Corticotropin)
  • TSH (Thyroid-Stimulating Hormone or Thyrotropin)
  • PRL (Prolactin or Luteotropic hormone (LTH)
  • GH (Growth Hormone)
  • FSH (Follicle-Stimulating Hormone)
  • LH (Luteinizing Hormone)

Posterior pituitary

  • Oxytocin
  • ADH(AntiDiuretic Hormone or Vasopressin)

Hypothalamo-pituitary

Gonadotropins:

  •  LH (Luteinizing Hormone)
  • FSH (Follicle Stimulating Hormone)
  • HCG (Human Chorionic Gonadopropin)

Gonads Glands

(Ovaries or Testes)

  • Testosterone
  • Estradiol
  • Antimullerian Hormone
  • Progesterone
  • Inhibin B and Activin