Lecture 19

Question 1

Describe the structural relationship between the hypothalamus and pituitary gland

Answer 1

The pituitary gland sits in the sella turcica at the base of the skull
The hypothalamus drops down through the infundibulum to form the posterior pituitary

Question 2

Where are neurohormones stored?

Answer 2

A region called the median eminence situated just above the anterior pituitary

Question 3

What are the hormone produced by the hypothalamus and what are their functions?

Answer 3

Trophic peptide hormones:
• TRH Thyrotrophin Releasing Hormone
• PRH Prolactin Releasing Hormone
• PIH Prolactin Release-Inhibiting Hormone
• CRH Corticotrophin Releasing Hormone
GnRH Gonadotrophin Releasing Hormone
• GHRH Growth Hormone Releasing Hormone
• SS Somatostatin (or GHIH, Growth hormone inhibitory hormone)
Peptide hormones to be released by the posterior pituitary gland
• OT Oxytocin (Milk “let down” during suckling and uterus contractions during child birth)
• ADH Antidiuretic hormone (Regulation of body water volume)

Question 4

What are the peptide hormones produced by the anterior pituitary gland and what are their functions?

Answer 4

• TSH Thyroid stimulating hormone (trophic). Stimulates secretion of thyroid hormone from the thyroid gland
• ACTH Adrenocorticotrophic hormone (trophic). Secretion of hormones from adrenal cortex)
• LH Luteinizing hormone (trophic). Ovulation and secretion of sex hormones)
• FSH Follicle stimulating hormone (trophic). Development of eggs and sperm)
• PRL Prolactin (mammary gland development and milk secretion)
• GH Growth hormone (growth and energy metabolism) AND synthesis of IGFs in the liver and skeletal muscle (trophic).)

Question 5

What produces, stimulates and inhibits growth hormone?

Answer 5

Produced in the pituitary gland
Stimulated by Growth hormone releasing hormone
Inhibited by somatostatin

Question 6

How is GH secretion regulated?

Answer 6

• A decrease in glucose of fatty acid leads to an increase in GH secretion.
• An increase in glucose or free fatty acid leads to a decrease in GH secretion.
• Fasting increases GH secretion whereas obesity leads to a reduction in GH secretion.
• There is a surge in GH secretion after onset of deep sleep
• Light sleep (Rapid Eye Movement (REM) sleep) inhibits GH secretion
• Stress (e.g. trauma, surgery fever) increases GH secretion
• Exercise increases GH secretion

Question 7

What is the long loop negative feedback mechanism?

Answer 7

Mediated by IGF’s
Inhibit the release of GHRH
Inhibit the action of GHRH in the anterior pituitary.
Stimulates the release of somatostatin

Question 8

What is the short loop negative feedback mechanism?

Answer 8

Mediated by GH itself via the stimulation of somatostatin release.

Question 9

How does GH exert its effects on cells?

Answer 9

The GH receptor is a cytokine receptor, coupled to Janus kinases. Activation of a transcription factor that turns on production of IGFs.

Question 10

What are the two known forms of IGF’s in mammals and where are they produced?

Answer 10

IGF-1 and IGF-2 produced in the liver and skeletal muscle