The Anterior Lobe of Pituitary Gland - Practice Questions & MCQ

• Pituitary gland develops from the ectoderm.
• It is the 'Master Endocrine Gland' or 'Chief Executive of Endocrine system or 'the leader of Endocrine Orchestra' because its hormones control other parts of Endocrine system
• It is located just below the hypothalamus located in a bony cavity called Sella turcica of the sphenoid bone of the skull
• It is attached to the brain by a stalk called the infundibulum which is in continuation with the hypothalamus.
• The pituitary gland is made up of two main lobes of different origin :
  • Larger anterior lobe or adenohypophysis or pars distalis
  • Smaller posterior lobe  or neurohypophysis or pars nervosa
• Adenohypophysis originates as Rathke's pouch from dorsal wall of stomodaeum in the embryo while Neurohypophysis originates as an outgrowth from the floor of diencephalon
• There is a third lobe called the intermediate lobe or pars intermedia. It is a part of the adenohypophysis.

Adenohypophysis 

• It comprises about 75% part of the gland
• Hypothalamic hormones are secreted by neurons but enter the anterior pituitary through blood vessels.
• Within the infundibulum is a bridge of capillaries that connects the hypothalamus to the anterior pituitary. 
• This network, called the hypophyseal portal system, allows hypothalamic hormones to be transported to the anterior pituitary without first entering the systemic circulation.

Hormones of Adenohypophysis:

1. Growth Hormone (GH):

• This is also called as somatotrophic hormone (STH). 
• It stimulates the growth of bones, cartilages, muscles, visceral organs and the body as a whole. 
• It also promotes protein synthesis, intestinal calcium absorption and glycogenolysis.

2. Adrenocorticotropic Hormone (ACTH):

• This hormone is a tropic hormone i.e. influences the activity of another endocrine gland.
• Here the target endocrine gland is cortex of adrenal gland which is stimulated to produce glucocorticoids. 
• ACTH is secreted in greater amounts during emotional and physical stress.

3. Thyroid Stimulating Hormone (TSH):

• Also known as Thyrotropic hormone (TTH) or Thyrotrophin. It controls the growth and activity of the thyroid gland. 
• It also stimulates the thyroid gland to synthesise thyroxine and release it into the blood.

4. Follicle Stimulating Hormone (FSH):

• It is a gonadotropic hormone. 
• In females, it stimulates the ovaries to develop and maturation of ovarian follicles. 
• The same hormone in males stimulates testes for development of seminiferous tubules and spermatogenesis. 
• Due to its action on both male and female gametes, FSH is also called Gametokinetic factor.

5. Luteinizing Hormone (LH):

• This is another gonadotropic hormone and is also known as Interstitial Cell Stimulating Hormone’ (ICSH). 
• In females, this hormone promotes final maturation of ovarian follicle, ovulation and formation of corpus luteum. 
• In males, it stimulates the interstitial cells of testes causing them to release male sex hormones (androgens).

6. Prolactin (PRL) or Mammotropin Hormone or Luteotrophic Hormone:

• It stimulates the growth of mammary glands in females during pregnancy and initiates secretion of milk after childbirth.

Intermediate Lobe:

• It produces only one hormone i.e. Melanocyte Stimulating Hormone (MSH) or Intermedin. 
• This hormone is responsible for the synthesis of melanin pigment in melanophore or melanocyte cells. 
• It also brings about the dispersion of melanin pigments in melanophore cells and the darkening of the skin is affected.