Physiology IV

Question 1

What inhibits production of 1,25-(OH)2?

Answer 1

Increased 1,25-(OH)2 concentration. Feedback inhibits its own production (p.294)

Question 2

What does vitamin D deficiency cause in adults?

Answer 2

Osteomalacia (p.294)

Question 3

What does vitamin D deficiency cause in children?

Answer 3

Rickets (p.294)

Question 4

What is 24,25-(OH)2D3?

Answer 4

An inactive form of vitamin D (p.294)

Question 5

What is the difference in calcium and phosphate absorption due to PTH action compared to 1,25-(OH)2 action?

Answer 5

PTH: increases Ca2+ reabsoprtion and decreases phosphate reabsorption in the kidney; 1,25-(OH)2: causes increased absorption of both Ca2+ and phosphate in the gut (p.294)

Question 6

What is the source of Calcitonin?

Answer 6

Parafollicular cells (C cells) of the thyroid (p.294)

Question 7

What is the function of Calcitonin?

Answer 7

To decrease bone resorption of calcium (p.294)

Question 8

How is calcitonin secretion regulated?

Answer 8

Increased serum calcium causes calcitonin secretion (p.294)

Question 9

What is the relationship between calcitonin and PTH?

Answer 9

Calcitonin opposes the actions of PTH (p.294)

Question 10

What is the significance of calcitonin in normal calcium homeostasis?

Answer 10

Calcitonin is not important in normal calcium homeostasis (p.294)

Question 11

Name the 12 endocrine hormones that act via cAMP signalling pathways.

Answer 11

FSH, LH, ACTH, TSH, CRH, hCG, ADH (V2 receptor), MSH, PTH, calcitonin, GHRH, glucagon (FLAT ChAMP + CGG) (p.294)

Question 12

Name the 2 endocrine hormones that act via cGMP signalling pathways.

Answer 12

ANP, NO (EDRF) (think vasodilators) (p.294)

Question 13

Name the 8 endocrine hormones that act via IP3 signalling pathways.

Answer 13

GnRH, GHRH, Oxytocin, ADH (V1 receptor), TRH, histamine (H1), angiotensin II, gastrin (GGOAT HAG) (p.294)

Question 14

Name the 8 endocrine hormones that act via steroid receptor signalling pathways.

Answer 14

Vitamin D, Estrogen, Testosterone, T3, T4, Cortisol, Aldosterone, Progesterone (VETTT CAP) (p.294)

Question 15

Name the 5 endocrine hormones that act via intrinsic tyrosine kinase receptor signalling pathways.

Answer 15

Insulin, IGF-1, FGF, PDGF, EGF (p.294)

Question 16

Name the 3 endocrine hormones that act via receptor associated tyrosine kinase signalling pathways.

Answer 16

Prolactin, Immunomodulators (e.g. cytokines IL-2, IL-6, IL-9, IFN), GH (PIG) (Includes JAK/STAT pathway, acidophiles, and cytokines) (p.294)

Question 17

How do steroid hormones circulate in the blood?

Answer 17

Bound to specific binding globulins to increase their solubility as they are lipophilic (p.295)

Question 18

What is the effect of increased sex hormone binding globulin (SHBG) in men?

Answer 18

Lowers free testosterone causing gynecomastia (p.295)

Question 19

What is the effect of decreased sex hormone binding globulin (SHBG) in women?

Answer 19

Raises free testosterone causing hirsutism (p.295)

Question 20

When do SHBG levels increase in women?

Answer 20

During pregnancy (p.295)

Question 21

Describe the signalling mechanism of steroid hormones.

Answer 21

The hormone binds to its receptor in the nucleus or cytoplasm. The receptor is transformed to expose its DNA binding domain. The receptor/hormone complex binds to its inhancer-like element of DNA in the nucleus. This triggers gene transformation to pre-MRNA –> mRNA (which leaves the nucleus)–> protein –> response (p.295)

Question 22

What is the general structure and function of T3/T4?

Answer 22

Iodine containing thyroid horomones that control the body’s metabolic rate (p.295)

Question 23

What is the source of T3/T4?

Answer 23

Follicles of the thyroid (p.295)

Question 24

Where is most T3 formed?

Answer 24

In target tissues (p.295)

Question 25

What are the two principle functions of T3 and T4?

Answer 25

To stimulate bone growth in synergysm with GH and CNS maturation (p.295)