Principles and Scope of Endocrinology

Question 1

What is a hormone?

Answer 1

• A substance produced by one organ, conveyed by circulation to another organ and regulates level of function of a TARGET ORGAN

Question 2

What do the following glands do:
- Hypothalamus
- Pituitary
- Thyroid
- Parathyroid
- Adrenals
- Pancreas
- Gonads

Answer 2

• Region controlling pituitary gland
• Secretes hormones affecting the behaviour of other glands
• Affects metabolism
• Regulates calcium levels in blood
• Triggers fight or flight response
• Regulates level of sugar in blood
• Secretes sex hormones

Question 3

Describe end product inhibition.

Answer 3

End-product inhibition is when the final product inhibits an enzyme involved in the initial reactions.

Question 4

What happens in the PTH-calcium feedback loop?

Answer 4

• Parathyroid hormone (PTH) stimulates release of calcium from bone
• Plasma calcium level rises
• High calcium inhibits PTH secretion

Question 5

What are some ways of negative feedback can work?

Answer 5

• Increase or decrease in circulating component stimulates or inhibits endocrine gland
• Hormone acts directly on neuroendocrine cells and pituitary gland and either stimulates or inhibits production

Question 6

What are some ways things can go wrong during endocrine disease?

Answer 6

• Autoimmune disease leading to glandular damage
• Hormone deficiencies or excess
• Overactivity of gland
• Autonomous hormone secretion without regulation or feedback

Question 7

What can autoimmune thyroid diseases and thyroid adenomas lead to?

Answer 7

TSH Suppression and rise in thyroxine levels

Question 8

What are the consequences of diabetes?

Answer 8

• Impaired glucose regulation
• Increased risk of vascular disease - e.g heart, brain, feet
• Tissue damage caussed by hyperglycaemia - neuropathy (feet), renal failure and retinopathy

Question 9

Go to slide 31.
What is the condition pictured?
Which gland is the cause?
What is the mechanism of the abnormality?

Answer 9

• Acromegaly
• Growth hormone secreting pituitary adenoma
• IGF-1 is produced in response to GH. IGF-1 mediates the effects of GH and has a negative feedback effect to inhibit GH secretion by producing somatostatin and acting on somatotrophs - negative feedback loop is removed in those with acromegaly causing raised GH

Question 10

Go to Slide 31.
Which systems are affected?
What treatment is available?

Answer 10

• Cardiovascular system, GI (can increase risk of colonic polyps), MSK (osteoarthritis)
• Surgical removal of the pituitary adenoma via transsphenoidal surgery, somatostatin analogues to inhibit GH release, dopamine agonists - suppress GH secretion by binding to dopamine receptor, complication monitoring and disease activity monitoring

Question 11

Compare and contrast hormone secretion and neurotransmitter release.

Answer 11

• Hormones are produced in endocrine glands and are released into the blood stream and act on distal sites
• Neurotransmitters are released into the synaptic gap by a terminal of a stimulated presynaptic nerve cell, transmitting a nerve signal to its neighboring postsynaptic nerve cell - faster