Endocrinology - Lecture 3

Question 1

What is the parathyroid hormone secreted from?

Answer 1

parathyroid chief cells in the thyroid

Question 2

How many parathyroid glands are there and where are they located?

Answer 2

4, located on the back side of the thyroid

Question 3

What happens to plasma calcium levels when parathyroids are removed?

Answer 3

there is a severe drop = convulsions and death

Question 4

What is the structure of parathyroid hormone?

Answer 4

N-terminal 34 amino acid

Question 5

What is the larger protein that undergoes proteolytic cleavage to produce parathyroid hormone?

Answer 5

preproparathyroid hormone

Question 6

What is the half-life of parathyroid hormone?

Answer 6

3-18 minutes

Question 7

What is the main function of the parathyroid hormone?

Answer 7

increase the concentration of plasma calcium

Question 8

What does PTH do to bone resorption?

Answer 8

it increases bone demineralization

Question 9

What does PTH do to the kidneys?

Answer 9

it increases the reabsorption of Ca++ in proximal convoluted tubule

Question 10

What does PTH do to vitamin D synthesis?

Answer 10

stimulates the conversion of 25-hydroxyvitamin D3 to 1,25-dihydroxyvitamin D3

Question 11

Where does PTH stimulate the conversion of 25-hydroxyvitamin D3 to 1,25-dihydroxyvitamin D3?

Answer 11

in the kidney

Question 12

What does PTH do to the gut?

Answer 12

it facilitates the absorption of Ca++ from the gut

Question 13

What does PTH use in the gut to facilitate the absorption of Ca++?

Answer 13

1,25D3

Question 14

What controls PTH release?

Answer 14

the circulating concentration of calcium

Question 15

What is the mechanism of PTH activity?

Answer 15

it binds to cognate receptor on target cells

Question 16

What is hypoparathyroidism?

Answer 16

low levels of PTH in circulation

Question 17

What are the 3 symptoms of hypoparathyroidsim?

Answer 17

1. hypocalcemia
2. decreased vitamine D production
3. tetany

Question 18

What level of calcium needs to be present in the body for there to be muscle spasms in hypoparathyroidism?

Answer 18

<7mg/100mL

Question 19

What is the treatment for hypoparathyroidism?

Answer 19

administration of 1,25-dihydroxyvitamin D and calcium supplements

Question 20

What is hyperparathyroidism?

Answer 20

parathyroid adenoma of parathyroid producing too much PTH

Question 21

What two substances are produced too much in hyperparathyroidism?

Answer 21

1. PTH
2. 1,25D3

Question 22

What does high PTH stimulate in hyperparathyroidism?

Answer 22

bone resorption and calcium reabsorption from the kidney

Question 23

What does 1,25D3 increase in hyperparathyroidism?

Answer 23

calcium absorption from the intestines

Question 24

How are the levels of calcium describes in hyperparathyroidism?

Answer 24

elevated

Question 25

What is a common symptom of hyperparathyroidism?

Answer 25

kidney stones

Question 26

What are the symptoms of severe cases of hyperparathyroidism?

Answer 26

cardiac arrhythmias, depressed neuromuscular excitability, calcium deposition on walls of blood vessels and cartilaginous regions of bones

Question 27

What is the treatment for hyperparathyroidism?

Answer 27

removal of affected parathyroids and replacement therapy of 1,25D3 and Ca++

Question 28

How can we get vitamin D from our diet?

Answer 28

cod liver oil, fatty fish

Question 29

Why is vitamin D not a vitamin?

Answer 29

because it can be synthesized from a cholesterol metabolite

Question 30

What are the 3 steps in the synthesis of vitamin D?

Answer 30

1. UVB light + 7-dehydrocholesterol in the skin 2. 25-hydroxylation in liver 3. 1-hydroxylation in kidney and several peripheral tissues -> 1,25-dihydroxyvitamin D3

Question 31

What is the primary function of vitamin D?

Answer 31

increases calcium absorption from the intestine

Question 32

What are the 2 secondary functions of vitamin D?

Answer 32

1. regulates immune system (protects against infection, anti-inflammatory) 2. anticancer properties

Question 33

When is vitamin D synthesis increases?

Answer 33

in conditions of low calcium when PTH is also increases

Question 34

When is vitamin D synthesis decreased?

Answer 34

when calcium is high

Question 35

What is Rickets?

Answer 35

absence fo UVB leading to vitamin D deficiency and deficient bone mineralization

Question 36

What does low vitamin D lead to in adults?

Answer 36

osteomalacia

Question 37

What is calcitonin made of?

Answer 37

32 amino-acid calcium-loweing peptide hormone

Question 38

Where is calcitonin manufactured?

Answer 38

in parafollicular cells of the thyroid gland

Question 39

What is the function of calcitonin?

Answer 39

lowers plasma calcium

Question 40

How does calcitonin lower plasma calcium?

Answer 40

1. promoting transfer of Ca++ from blood to bone 2. increasing urinary excretion of Ca++

Question 41

Rise in plasma Ca++ ___ the release of calcitonin.

Answer 41

increases

Question 42

Decrease in plasma calcium concentration ___ the release of calcitonin.

Answer 42

decreases

Question 43

Calcitonin is of ___ importance than PTH and 1,25D3.

Answer 43

lesser

Question 44

Does the absence of calcitonin compromise calcium homeostasis?

Answer 44

no

Question 45

Where are adrenal glands located?

Answer 45

adjacent to the upper surface of the kidneys

Question 46

Are adrenal glands heavier in males or females?

Answer 46

males

Question 47

What are the 2 tissues found in the adrenal glands?

Answer 47

cortex and medulla

Question 48

What is the histologic appearance of the cortex?

Answer 48

large-lipid containing epithelial cells

Question 49

What is the histologic appearance of the medulla?

Answer 49

chromaffin cells-fine brown granules when fixed with potassium bichromate

Question 50

What is the origin of the cortex?

Answer 50

derived from mesoderm

Question 51

What is the origin of the medulla?

Answer 51

derived from the neural crest

Question 52

What is the function of the cortex?

Answer 52

produces steroid hormones

Question 53

What are the 3 hormones that the cortex produces?

Answer 53

1. glucocorticoids 2. mineralocoirticoids 3. progestins

Question 54

What are the 4 hormones that the medulla produces?

Answer 54

1. catecholamines 2. epinephrine 3. norepinephrine 4. some peptide hormones

Question 55

What are the 3 layers of the adrenal cortex called?

Answer 55

1. zona glomerulosa 2. zona fasciculata 3. zona reticularis

Question 56

What does the zona glomerulosa produce?

Answer 56

mineralocorticoids (aldosterone)

Question 57

What does the zona fasciculata produce?

Answer 57

glucocorticoids (cortisol)

Question 58

What does the zona reticularis produce?

Answer 58

glucocorticoids, progestins, androgens and estrogens

Question 59

What is the synthesis of adrenal steroids controlled by?

Answer 59

adrenocorticotropin ACTH

Question 60

Which zone is 18-hydroxylase present in?

Answer 60

zona glomerulosa

Question 61

Which zone is 17a-hydroxylase not present in? Why?

Answer 61

zona glomerulosa, because this zone does not produce glucocorticoids

Question 62

What is the function of steroid hormones?

Answer 62

to regulate the transcription of hormone/receptor specific target genes

Question 63

What are the 2 functions of aldosterone?

Answer 63

1. increases the reabsorption of Na+ by the kidney 2. affects the plasma concentration of K+ and H+

Question 64

What is an example of a glucocorticoid?

Answer 64

cortisol (humans), corticosterone (rodents)

Question 65

Which steroid hormone has more of an effect on salt retention?

Answer 65

aldosterone > cortisol

Question 66

How do glucocorticoids have an effect on protein and carbohydrate metabolism?

Answer 66

stimulate the synthesis of a number of gluconeogenic enzymes in hepatocytes, and several enzymes that breakdown proteins in muscle and other tissues

Question 67

What does cortisol do to gluconeogenesis and glucose oxidation?

Answer 67

gluconeogenesis: increased glucose oxidation: decreased

Question 68

Since glucocorticoids increase blood glucose levels, what happens to secreted insulin?

Answer 68

it increases

Question 69

What is increased blood glucose due to excess of glucocorticoid activity known as?

Answer 69

adrenal diabetes

Question 70

What happens if adrenal diabetes is prolonged?

Answer 70

it leads to true diabetes mellitus

Question 71

What do glucocorticoids do to the levels of lipolytic enzymes in the adipose tissue cells?

Answer 71

they maintain or increase them

Question 72

What does excess of glucocorticoids lead to in lipid metabolism?

Answer 72

hyperlipidemia and hypercholesterolemia

Question 73

What do glucocorticoids do to 1. inflammatory responses 2. atrophy of the lymphatic system 3. circulating lymphocytes 4. antibody formation 5. histamine formation

Answer 73

1. decrease 2. increase 3. decrease 4. decrease 5. decrease

Question 74

What steroid hormone is used in organ transplantation?

Answer 74

glucocorticoids

Question 75

Through the protein catabolic effect of glucocorticoids, what do they do to the protein matrix of bones?

Answer 75

they decrease it

Question 76

What does glucocorticoids increase the loss of in bone which can lead to osteoporosis?

Answer 76

Ca++

Question 77

What is ACTH synthesized as part of?

Answer 77

proopiomelanocortin (POMC)

Question 78

What controls the feedback of cortisol secretion? (2)

Answer 78

hypothalamus and anterior pituitary

Question 79

What happens to ACTH secretion in cases of enzyme deficiencies?

Answer 79

it is unchecked

Question 80

What is caused due to enzyme deficiencies where cortisol is not produced?

Answer 80

congenital adrenal hyperplasia

Question 81

What is the treatment for congenital adrenal hyperplasia?

Answer 81

administration of cortisol

Question 82

Why is administration of cortisol used to treat congenital adrenal hyperplasia?

Answer 82

a) it corrects the deficiency b) normalizes the ACTH secretion

Question 83

What 2 membranes does ACTH bind to?

Answer 83

zona fasciculata and zona reticularis

Question 84

What causes an increased production of cyclic AMP?

Answer 84

stimulation of adenylyl cyclase

Question 85

What does cyclic AMP activate?

Answer 85

steroidogenic enzymes

Question 86

What happens when steroidogenic enzymes are activated?

Answer 86

increase in synthesis and release of steroid hormones

Question 87

When is the diurnal rhythm of ACTH and cortisol secretion at a minimum and maximum?

Answer 87

minimum: midnight maximum: in the morning

Question 88

What can the rhythm of plasma cortisol and ACTH be abolished by?

Answer 88

stress and Cushing's disease

Question 89

What does stress stimuli (physical or psychological) increase the synthesis and release of?

Answer 89

CRH, ACTH and cortisol

Question 90

Why can the release of cortisol during stress be advantageous?

Answer 90

because it provides energy and amino acids through the breakdown of tissue proteins

Question 91

Why can the release of cortisol during stress be disadvantageous?

Answer 91

because it can inhibit wound healing

Question 92

Prolonged stress would maintain high levels of ___ which could lead to increased ___ ___, decreased ___ ___ and ___ ___

Answer 92

glucocorticoids, blood glucose, immune responses, bone loss