B1: RMcC Endocrinology Path + Physiology I and II

Question 1

How do hormones act upon target tissues?

Answer 1

Actually undergo ‘blind targeting’ -> hormones are disseminated in blood and thus can technically affect target and non-target organs (anything with appropriate receptor)

1. Non-Cell-Entering Hormones (e.g. insulin)
   - bind to cell surface receptors
   - trigger intracellular second messengers
   - carries out action (e.g. for insulin, results in expression of GLUT receptors for glucose uptake)
2. Cell-Entering Hormones (e.g. oestrogen)
   - Bind to Intracellular receptors that funtion in the cell nucleus
   - Alter gene expression

Question 2

Which hormones enter cells?

Answer 2

Oestrogen & Testosterone
Aldosterone
Progesterone 
Cortisol
Vit D

Question 3

Which hormones don’t enter cells?

Answer 3

Insulin
Insulin-like growth factor
Growth Hormones
Prolactin
Thyroid Hormones

Question 4

How is the endocrine system regulated?

Answer 4

Via feedback loops

I.e. -> output from Hypothalamus triggers hormone release from Pituitary glands, which act upon target tissues and/or other endocrine organs in the body

• > can cause further release of hormones
• > Hormones tend to feed back to ‘higher-up’ processes (e.g. the hypothalamus or pituitary) to either enhance or inhibit the secretion of hormones

Question 5

What results from decreased iodine?

Answer 5

Decreased T3 and T4 production by thyroid

Leads to enlargement of thyroid tissue -> GOITER

Question 6

What hormones are secreted by the POSTERIOT Pituitary?

What is interesting about the secretion of hormones from the PP?

Answer 6

Oxytocin:

• acts on ovaries and mammary glands
• contractions and lactation

ADH (vasopressin, whatever):

• Acts on kidneys, arterioles
• Decreased water loss through kidneys, vascocontriction to increase BP

**Hormones secreted by the posterior pituitary are actually synthesized by the hypothalamus ->

Question 7

Which nuclei control release of hormones from Posterior Pituitary?

Answer 7

Supraoptic and Paraventricular (hypothalamus)

Question 8

What hormones are secreted by anterior pituitary?

Answer 8

Thyroid Stimulating Hormone (TSH):

• Stimulares secretion of T3 and T4 from thyroid
• Metabolic regulation, protein synthesis, etc.

ACTH
- Stimulates corticol (and other glucocorticoids) release from Adrenal Cortex

FSH

• Targets Gonads
• Reproductive system growth (follicular growth, endometrial growth)

LH

• Targets Gonads
• Production of Sex Hormones

Endorphins:

• Target Pain Receptors in the Brain
• Act as Opioid - reduction of pain

Prolactin:

• Targets Ovaries and Mammary Glands
• Stimulates Oestrogen/Progesterone Secretion by Ovaries and Milk Production by Mammary Glands

Question 9

What key hormones have a cyclic relationship that follows the circadian rhythm?

Answer 9

Cortisol: Peaks upon rising, then declines throughout the day (with two smaller surges every 6 hours during waking)

Testosterone: Peaks with rising, declines steadily throughout day

Growth Hormone: Large and Small peaks throughout the day. Large peaks highly concentrated during the night, more in younger people. Older people have less Large Peaks of release.

Question 10

What is an Endocrine Stimulation Test?

Answer 10

Used when patient suspected of producing too little of a hormone
Administer a hormone which should increase production of that hormone

E.g. Addison’s disease -> Cortisol deficiency secondary to adrenal insufficiency

Test: Administer ACTH -> If cortisol rises in response, then adrenal insufficiency is excluded as a cause

Question 11

What is an endocrine suppression test?

Answer 11

Used when patient suspected of over-producing a hormone
Administer hormone which should suppress that hormone

E.g. Cushings Disease -> caused by too much cortisol secondary to over-secretion of ACTH by Anterior Pituitary

Administer Dexamethasone -> If cortisol levels remain elevated (>50mmol/L) the Cushing’s Disease is indicated

E.g. Acromegaly -> caused by too much GH

Administer Glocose load (75-100g), and measure GH after 2 hours
GH >1ug/L is abnormal

Question 12

What are the limits for Glucose Tolerance Testing?

Answer 12

Impaired Fasting Glucose:

Fasting Glucose 6.1-6.9 AND 2-hr glucose or equal to 7.0 OR 2-hr Glucose >or equal to 11.1

Question 13

How does diabetic retinopathy occur?

Answer 13

Small blood vessels, such as those in the retina, are susceptible to damage from glucose and fructose

Glucose initiates pathway that results in pericyte apoptosis

Ensuing damage to blood vessels and inflammation occurs

Lasting damage to retina occurs due to ongoing inflammation and vascular remodelling cycles

Results in vision changes or blindness

Question 14

What is the Thrifty Phenotype?

Answer 14

Hypothesis that associates poor fetal nutrition with various chronic illnesses later in life: chiefly, diabetes, hypertension, CAD, etc.

From evolutionary perspective, thought that fetuses exposed to poor nutrition would make adjustments necessary for them to cope with ongoing life in similar circumstances. Thus, those born with poor nutrition whom are then exposed to good nutrition tend to become obese and develop metabolic disorders and other health issues

Poor Materal Nutrition -> Poor Fetal Nutrition. This leads to:

1. Organ Malfunction (e.g. Liver) -> leads to Metabolic Disorder
2. Amino Acid Changes -> Could affect glucose Tolerance -> Perpetuating Obesity -> Metabolic Disorder
3. Hypertension -> Feeds into Metabolic Disorder

Question 15

Endocrine Functions of Adipocytes?

Answer 15

Produce:

• LEPTIN -> ‘satiety’, ACTH and TSH release
• Complement Factors and TNF-a -> Inflammation
• RESISTIN -> Increases LDL and decreases statin efficacy
• ANGIOTENSINOGEN -> HTN
• FFA -> High cholesterol etc
• Cortisol