Pituitary gland

Summary

The pituitary gland, also known as the hypophysis, is considered the “master endocrine gland” because it releases hormones that regulate the activity of multiple major endocrine organs in the body. The gland sits on the sella turcica, just below the hypothalamus , which is the primary regulator of the pituitary gland. The pituitary gland has 2 lobes: the anterior lobe (the adenohypophysis) and the posterior lobe (the neurohypophysis). Each lobe has its own regulation, set of secretory products, and feedback loops. Abnormalities in the pituitary gland can lead to a wide range of clinical conditions, some of which include hyperprolactinemia , acromegaly , hyperthyroidism or hypothyroidism , and central diabetes insipidus .

Overview

The pituitary gland is known as the “master endocrine gland.” This gland receives stimulatory input from the hypothalamus and secretes multiple different hormones , which target multiple different end organs and have wide-ranging effects throughout the body.

Location

• Located in the sella turcica of the sphenoid bone
• Just below the optic chiasm
• Connected to the hypothalamus by the pituitary stalk
• Lies outside the dura

General structure  Consists of two major parts:

• Anterior pituitary gland (adenohypophysis): develops from oral ectoderm (Rathke pouch) and constitutes 80% of the pituitary.

• Posterior pituitary gland (neurohypophysis): develops from neural ectoderm

Development and Gross Anatomy

Development

Anterior pituitary:

• Develops from outpocket of the oropharynx (Rathke pouch)
• Derived from oral ectoderm

Posterior pituitary:

• Downgrowth from the 3rd ventricle of the brain
• Derived from neuroectoderm

Gross anatomy

Major components of the pituitary gland include:

• Pars distalis: the bulk of the glandular portion/anterior pituitary
• Pars nervosa: the bulk of the neurosecretory portion/posterior pituitary
• Pars intermedia: a thin wedge separating the pars distalis from the pars nervosa
• Pituitary stalk:
  • Connects the pea-like lobes of the pituitary (the pars distalis and the pars nervosa) to the hypothalamus
  • Consists of: 
    • Infundibulum: arises from the posterior pars nervosa
    • Pars tuberalis: arises from the anterior pars distalis and wraps around the infundibulum

Functions

• The anterior pituitary gland is responsible for the release of:
  1. Follicle-stimulating hormone (FSH)
  2. Luteinizing hormone (LH)
  3. Adrenocorticotropic hormone (ACTH)
  4. Thyroid-stimulating hormone (TSH)
  5. Prolactin (PRL)
  6. Growth hormone (GH)

• The posterior pituitary gland is responsible for the storage/release (تخزن الهرمونات ولا تقوم بتصنيعها) of the antiduiretic hormone (ADH) and oxytocin.

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