4: Anterior Pituitary Gland

The Hormones secreted by the Anterior Pituitary gland are classified as ?

• Tropic Hormones

• The term trophic means “feed or nourish”

high concentrations of trophic hormones results in hyper…?

• Hypertrophy target tissues.

stimulation of the target tissues by hormones of the anterior pituitary is necessary to?

• Maintain the mass of the tissue.

How many main hormones are released by the Anterior Gland?

• 6 Major

What are the 6 Major Hormones released by the Anterior P Gland?

• GH (Growth Hormone)

• TSH (Thyroid Stimulating Hormone)

• Adrenocorticotropic Hormone (ACTH)

• Follicle-Stimulating Hormone (FSH)

• Luteinising Hormone (LH)

• Prolactin

Describe GH?

• Growth Hormone also known as Somatotropin

• Promotes the movements of Amino Acids.

• Most Tissues are sensitive to GH

• About 40-50% of the cells in the anterior pituitary are composed of the GH producing cells

In response to stimulation by GH, the liver can produce a group of molecules called?

• Called Somatomedins that also encourage

• the growth of cartilage, bones and protein synthesis in muscle cells.

What is TSH?

• Thyroid Stimulating Hormone

• stimulates the thyroid gland to produce and secrete thyroxine (T4 & T3)

What is ACTH?

• Adrenocorticotropic Hormone (ACTH)

• Stimulates Adrenal Cortex to release glucocorticoids such as cortisol

What is FSH?

• Follicle-stimulating hormone

• Stimulates growth of ovarian follicles in females

• and stimulates the production of sperm in the testes of males

What is LH?

• Luteinising Hormone

• Stimulates Ovulation in Females.

• Converts an ovulated ovarian follicle into a structure

• called the corpus luteum, a temporary endocrine gland.

In males, LH is sometimes referred to as?

• “interstitial cell stimulating hormone” (ICSH)

• as it stimulates the release of sex hormones such as testosterone from the interstitial cells

• (Leydig cells) of the testes.

FSH & LH are collectively known as ….?hormones as they act upon the gonads

• Gonadotropins

• Gonads = Ovaries & Testes

What is Prolactin?

• stimulates the production of milk by the mammary glands in females after the birth of a baby

• Prolactin also supports regulation of the male reproductive system and acts on the kidneys to help regulate water/salt balance.

What is POMC?

• Pro-opiomelanocortin is a prohormone released from a small subset of cells

• result in the production of β-endorphin, melanocytestimulating hormone (MSH) and ACTH

The release of hormones from the anterior pituitary is controlled through?

• Hormonal Regulations

These regulatory hormones are produced and released by neurons of the?

• Hypothalamus

Neurons of the hypothalamus project axons to an area called the median…..?

• Eminence

• where regulatory hormones are released into the (primary) capillaries

However, the veins that drain blood from the capillaries of the median eminence do not?

• Go directly back to the Heart

Instead these veins deliver the venous blood into another?

• Capillary Bed

• 2nd Bed.

Veins that deliver blood from one capillary bed to another capillary bed act as a vascular link known as?

• Portal Veins

The vascular link between the hypothalamus and the anterior pituitary is known as the?

• hypothalamo-hypophyseal portal system

What is the effect of TRH on the Anterior Pituitary Gland?

• Thyrotropin-releasing hormone (TRH)

• Stimulates secretion of thyroid-stimulating hormone (TSH)

What is the effect of CRH on the Anterior Pituitary Gland?

• Corticotropin-releasing hormone (CRH)

• Stimulates secretion of adrenocorticotropic hormone (ACTH)

What is the effect of GnRH on the Anterior Pituitary Gland?

• Gonadotropin-releasing hormone (GnRH)

• Stimulates secretion of both follicle-stimulating hormone

• (FHS) and luteinizing hormone (LH)

What is the effect of GHRH on the Anterior Pituitary Gland?

• Growth hormone-releasing hormone (GHRH)

• Stimulates growth hormone secretion

What is the effect of Somatostatin on the Anterior Pituitary Gland?

• Inhibits secretion of growth hormone

What is the effect of Prolactin-inhibiting hormone on the Anterior Pituitary Gland?

• (Recently identified as the neurotransmitter dopamine)

• Inhibits prolactin secretion

Hormonal secretion of the anterior pituitary is largely controlled by what type of Feedback?

• Negative Feedback

TSH stimulates the thyroid to release?

• thyroxine (T4).

Increased levels of T4 in the blood act to inhibit the?

• Release of TSH 

• From the Anterior Pituitary Gland

Elevation of T4 in the blood also inhibits the release of?

• TRH

Reduced TRH and TSH secretion results in?

• reduced T4 production and secretion

increases in sex steroid hormone secretion from the gonads acts to inhibit the production of?

• FSH, LSH and GnRH

Castration removes the inhibition provided by the sex steroids resulting in a rise in secretion of?

• LH a & FSH

CTH stimulation of the adrenal cortex to secrete cortisol results in?

• Negative Feedback

Cortisol acts on the hypothalamus to?

• Inhibit CRH Secretion

Cortisol acts on the Anterior Pituitary to?

• inhibit ACTH secretion

Under stressful conditions there is an increase in the production of?

• ACTH

• From the Pituitary Gland.

• as a result of higher brain centre influence on the hypothalamus.

Surgical removal of the adrenal glands results in?

• Elevated ACTH Levels

The hypothalamus receives neural input from?

• Higher Brain Centres

As a result the pituitary-gonad and pituitary-adrenal axis can be influenced by?

• Emotions