IC1

Question 1

Define hormone

Answer 1

Hormones are substances secreted by endocrine glands and transported throughout the bloodstream to target tissues where they act to regulate specific functions.

Question 2

Can hormones exert its effect at very low concentrations? (Y/N)

Answer 2

Yes

Question 3

Exocrine vs Endocrine glands

Answer 3

• Exocrine glands produces non-hormonal substances and contains ducts that carry these substances to a membrane surface e.g. sweat and saliva glands
• Endocrine glands produces hormones which is released into surrounding tissue fluid (lacks ducts)

Question 4

2 types of endocrine glands + examples

Answer 4

1. Central - pituitary glands, hypothalamus
2. Peripheral - thyroid gland, adrenal gland, pancreas, ovary, testes

Question 5

Consequences of disrupting oestrogen (e.g. due to synthetic hormones)

Answer 5

1. Female: Increased incidence of breast tumour
2. Male: Reduced sperm count, cryptorchidism (undescended testis)
3. Animal: gender bending

Question 6

Characteristics of hormones bound to cell surface Vs intracellular receptors

Answer 6

Cell membrane receptors are usually bound to water-soluble, hydrophilic hormones Vs intracellular receptors are bound to lipid-soluble, hydrophobic hormones

Question 7

What could cause hormonal imbalances?

Answer 7

1. Excessive/ decreased secretion of hormones
2. Excessive/ decreased target cell responsiveness

Question 8

Intracellular events after binding hormones with a receptor

Answer 8

1. Alters channel permeability by acting on pre-existing channel forming proteins
2. Acts through second messenger system to alter activity of pre-existing proteins
3. Activates specific genes to cause formation of new proteins

Question 9

Where is the thyroid gland located?

Answer 9

Located in the neck, on the anterior surface of trachea, immediately below larynx

Question 9

Where is the thyroid gland located?

Answer 9

Located in the neck, on the anterior surface of trachea, immediately below larynx

Question 10

What are the two thyroid lobes connected by?

Answer 10

Isthmus

Question 11

Role of follicle cells, thyroid follicle & colloid

Answer 11

• Follicle cells: Synthesises thyroglobulin and secrete it into the colloid of the thyroid follicles
• Thyroid follicle: Functional unit for thyroid hormone production
• Colloid: Extracellular space that stores thyroglobulin with attached iodine atoms

Question 12

Role of parafollicular cells (AKA C cells)

Answer 12

Secrete calcitonin

Question 13

Basic ingredients of thyroid

Answer 13

1. Tyrosine aa (synthesised in body)
2. Iodine (obtained from diet and reduced to I- prior to absorption by small intestine)

Question 14

Key points of thyroid synthesis

Answer 14

1. Iodide trapping
2. Iodination
3. Coupling
4. Colloid resorption
5. Thyroglobin proteolysis

Question 15

___ is the major biologically active form of TH at the cellular level (10 times more potent than T4)

Answer 15

T3

Question 16

T4 (thyroxine) can get broken down into T3 (liver, kidney, pituitary) or inactive metabolite (liver, kidney) by ______.

Answer 16

5-deiodinase

Question 17

Physiological effects of T3 and T4

Answer 17

1. Controls rate of metabolism (BMR & thus heat production)
2. Sympathomimetic effect (Increased proliferation of catecholaminereceptor thus increased target cell responsiveness to catecholamines)
3. Cardiovascular effect (Increased heart responsiveness to catecholamines thus increased HR, force of contraction & CO)
4. Essential for normal bone growth and maturation
5. Crucial role in normal development of nervous system, especially the brain during childhood, and normal CNS activity in adults
6. Increased synthesis and degradation (metabolism) of proteins, lipids & carbohydrates

Question 18

Causes of hypothyroidism

Answer 18

1. Primary failure of thyroid gland
2. Secondary to deficiency of TSH, TRH or both
3. Inadequate supply of dietary iodine

Question 19

Key signs and symptoms of hypothyroidism

Answer 19

Intolerance to cold, weight gain, brittle nails & hair, constipation, dull-blank expression & extreme fatigue

Question 19

Key signs and symptoms of hypothyroidism

Answer 19

Intolerance to cold, weight gain, brittle nails & hair, constipation, dull-blank expression & extreme fatigue

Question 20

Causes of hyperthyroidism

Answer 20

1. Production of TSI
2. Secondary to excess of TSH, TRH or both
3. Hypersecreting thyroid tumour

Question 21

Key signs & symptoms of hyperthyroidism

Answer 21

Intolerance to heat, bulging eyes, enlarged thyroid, increased systolic BP, weight loss, muscle wasting, increased tremors & diarrhoea

Question 22

What is graves disease?

Answer 22

An autoimmune disease which causes body to erroneously secrete thyroid stimulating immunoglobulin (TSI). TSI binds to TSH receptor on thyroid cells and mimic the action of TSH –> leads to both secretion and growth of thyroid.

Question 23

What causes bulging of eyeball in graves disease?

Answer 23

Abnormal fluid retention behind eyeballs cause them to bulge forward (TSI stimulates release of cytokines, causing inflammation and oedema(?))

Question 24

Is TSI subjected to negative feedback inhibition by thyroid hormone? What is the consequence?

Answer 24

Unlike TSH, TSI is not subject to negative feedback inhibition by thyroid hormone --> thyroid secretion and growth remains unchecked

Question 25

Possible treatment options for hyperthyroidism

Answer 25

1. Anti-thyroid drugs that interfere with TH production (drugs that block I- uptake or inhibit TPO) 2. Surgical removal of a portion of hypersecreting thyroid gland 3. Administration of radioactive iodine

Question 26

What is goiter and its causes?

Answer 26

Enlarged thyroid gland; developed when thyroid gland is overstimulated by increased TSI / TSH 1. Hyperthyroidism: Increased TSH-TSI receptor activation 2. Hypothyroidism: Increased TSH but low iodine -> low TH synthesis -> high TSH remains -> thyroid growth

Question 27

Brief description of thyroid synthesis

Answer 27

The thyroid gland produces thyroid hormones by a process of concentration of iodine in the thyroid, iodination of tyrosine residues of Tg in the colloid space of the follicle, and endocytosis of colloid followed by proteolytic release of thyroid hormones T4 and T3.

Question 28

Pancreas is made up of an exocrine and endocrine portion (Y/N)

Answer 28

Yes

Question 29

Which cell secrete insulin and glucagon?

Answer 29

- alpha cells of islets of Langerhans of pancreas secrete glucagon - beta cells of islets of Langerhans of pancreas secrete insulin

Question 30

Biggest risk factor for type 2 diabetes

Answer 30

Obesity

Question 31

3Ps of acute consequences in insulin deficiency

Answer 31

1. Polyuria (excessive urine production) 2. Polydipsia (extreme thirst) 3. Polyphagia (excessive appetite/ eating)

Question 32

Example of microvascular complications in DM

Answer 32

Retinopathy, kidney failure, nerve damage

Question 33

Example of macrovascular complications in DM

Answer 33

Stroke, heart attack, reduced blood circulation

Question 34

Role of thyroperoxidase

Answer 34

1. Catalyses oxidation of Iodide to 'active' iodide 2. Attaches iodine to a tyrosine within Tg molecule

Question 35

Is MIT/ DIT of any endocrine value? (Y/N)

Answer 35

No

Question 36

What happens after endocytosis of colloid?

Answer 36

Lysosomes attack the engulfed vesicle and split the iodinated products from Tg

Question 37

Role of iodinase

Answer 37

Removes iodine from worthless MIT and DIT, allowing the freed iodide to be recycled for synthesis of more hormone

Question 38

Acute consequences of insulin deficiency

Answer 38

1. Increased hepatic glucose output 2. Decreased glucose uptake by cells 3. Decreased TG synthesis 4. Increased lipolysis 5, Decreased aa uptake by cells 6. Increased protein degradation

Question 39

3 consequences of dehydration caused by insulin deficiency

Answer 39

1. Polydipsia (excessive thirst) 2. Cellular shrinkage -> nervous system malfunction 3. Reduced blood volume -> peripheral circulatory failure -> low cerebral flow & renal failure -> death