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.

Anatomy of the Pituitary Gland

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

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

Figure: Diagram of Hypothalamic Pituitary Axis

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 anterior lobe is responsible for the production of six important hormones, which are secreted into the circulatory system (Blumenfeld 2002). The six hormones include:

  • Adrenocorticotropic Hormone (ACTH)
  • Growth Hormone (GH)
  • Thyroid Stimulating Hormone (TSH)
  • Luteinizing Hormone (LH)
  • Follicle Stimulating Hormone (FSH)
  • Prolactin (PRL)

These hormones serve to regulate endocrine systems in other areas of the body and are under the control of releasing factors from the hypothalamus, which include:

  • Growth Hormone-Releasing Hormone (GHRH) → GH release
  • Thyrotropin-Releasing Hormone (TRH) → TSH release
  • Gonadotropin-Releasing Hormone (GnRH) →  LH and FSH release
  • Corticotropin-Releasing Hormone (CRH) →  ACTH release
  • Prolactin-Releasing Factor (PRF) and TRH  →  PRL release
  • Somatostatin → decreases GH release

The posterior lobe contains the axons and nerve terminals of neurons which have their cell bodies in the hypothalamus. It is responsible for the secretion and storage of two hormones:

  • Vasopressin, or antidiuretic hormone (ADH), promotes water retention by absorbing water in the kidney tubules thereby concentrating urine.
  • Oxytocin allows for milk release in the breast and causes uterine contractions during labour.

Hormones Involved with the Neuroendocrine System

Following ABI, there may be notable changes in hormones released by the pituitary gland (Popovic et al. 2005). The hormones released by both the anterior or posterior pituitary glands and the accompanying bodily responses are listed in the table below.

Table: Pituitary Hormones and Bodily Responses

Glands

Hormones

Part of Body Affected

Body Response

Anterior Pituitary

PL

Mammary Gland

 

Lactation

ACTH

Adrenal Gland

 

Adrenalin

GH
 

Body Cells

 

Growth

TSH

Thyroid

 

Stimulation of growth and metabolism

FSH

 

Testes

 

 

 

 

Ovaries

 

Androgen production, sperm production,
testosterone secretion

LH

 

Ovum production,
estrogen and
progesterone secretion

Posterior Pituitary

ADH

Kidney

 

Water Regulation

Oxytocin

Uterus

 

Labour Contractions