Thyroid + adrenal physiology

Question 1

Which pattern of hormone secretion does cortisol follow?

Answer 1

Diurnal variation

Highest in the morning, lowest at night

Question 2

The thyroid spans which vertebral levels?

Answer 2

C4 - T1

Question 3

What is the basic structural and functional unit of the thyroid?

Answer 3

Follicles

Question 4

Where in the thyroid are hormones stored?

Answer 4

Colloid-filled lumen

Question 5

What do the parafollicular cells secrete?

Answer 5

Calcitonin

Question 6

Which 2 molecules form the thyroid hormones?

Answer 6

Tyrosine (thyroglobulin)

Iodine

Question 7

Which is secreted in larger quantities by the thyroid gland, T3 or T4?

Answer 7

T4

Question 8

Which is more biologically active, T3 or T4?

Answer 8

T3

Question 9

How is iodide taken up into the follicular cells from the blood?

Answer 9

Sodium-iodine symporter (NIS)

Question 10

What happens to iodide once it’s transported into the follicular lumen?

Answer 10

It is oxidised by thyroid peroxidase to form iodine

Question 11

In the thyroid, what is organification?

Answer 11

When iodine combines with thyroglobulin to form MIT and DIT

Question 12

Which enzymes oxidises iodide to iodine?

Answer 12

Thyroid peroxidase

Question 13

How are T3 and T4 transported into the follicular cells upon stimulation of the thyroid gland?

Answer 13

Endocytosis

Question 14

What is the daily recommended intake of iodine?

For pregnant women?

Answer 14

150 micrograms

200 micrograms

Question 15

Which foods are the main sources of iodine?

Answer 15

Milk / dairy products

Question 16

Which hormone in the HPT axis does the hypothalamus secrete?

Answer 16

Thyrotropin-releasing hormone (TRH)

Question 17

TRH stimulates which hormone to be released and from where?

Answer 17

Thyroid-stimulating hormone (TSH) from the anterior pituitary

Question 18

Describe what changes occur in the HPT axis which enables negative feedback.

Answer 18

Free T3 down-regulates TRH receptors on the anterior pituitary, decreasing TSH secretion

Question 19

What is the effect of oestrogen and adrenaline on thyroid hormone secretion?

Answer 19

Increase thyroid hormone secretion

Question 20

What is the effect of somatostatin and glucocorticoids on thyroid hormone secretion?

Answer 20

Inhibit thyroid hormone secretion

Question 21

Describe how thyroid hormones are transported in the blood.

Answer 21

70% bound to thyroid-binding globulin (TBG)

30% bound to albumin

Question 22

Which enzyme converts T4 into T3?

Answer 22

Deiodinase

Question 23

Under what conditions would T3 production decrease and reverse T3 production increase?

Answer 23

Stress conditions - low energy stores, fasting, illness

Question 24

Thyroid hormones increase oxygen consumption in all tissues except for which 3?

Answer 24

Brain
Gonads
Spleen

Question 25

What is the pathophysiology of Grave's disease?

Answer 25

Autoantibodies which stimulate the TSH receptor

Question 26

Give 2 causes of primary hypothyroidism.

Answer 26

Hashimoto's thyroiditis (autoimmune) Iodine deficiency

Question 27

What are the 2 distinct tissue parts of the adrenal gland, with percentages?

Answer 27

Medulla - 20% Cortex - 80%

Question 28

Adrenaline and noradrenaline are secreted from which part of the adrenal gland?

Answer 28

Medulla

Question 29

Corticosteroid hormones are secreted from which part of the adrenal gland?

Answer 29

Cortex

Question 30

What are the 3 layers of the adrenal cortex, from inner to outer?

Answer 30

Zona reticularis Zona fasciculata Zona glomerulosa

Question 31

Which layer of the adrenal cortex secretes aldosterone?

Answer 31

Zona glomerulosa

Question 32

Which layer of the adrenal cortex secretes cortisol?

Answer 32

Zona fasciculata

Question 33

In the synthesis of steroid hormones, what is cholesterol converted into and by which enzyme?

Answer 33

Pregnenolone, by desmolase

Question 34

Where in the cell does the conversion of cholesterol into pregnenolone occur?

Answer 34

Mitochondria

Question 35

In the synthesis of steroid hormones, what is pregnenolone converted into?

Answer 35

Progesterone

Question 36

Which hormone in the HPA axis does the hypothalamus secrete?

Answer 36

Corticotropin-releasing hormone (CRH)

Question 37

CRH stimulates which hormone to be released and from where?

Answer 37

Adrenocorticotropic hormone (ACTH) from the anterior pituitary

Question 38

Describe how cortisol is transported in the blood.

Answer 38

80% bound to cortisol-binding protein 15% bound to albumin 5% unbound + biologically active

Question 39

Does cortisol promote or inhibit gluconeogenesis?

Answer 39

Promotes gluconeogenesis

Question 40

Does too much cortisol result in hyper or hypoglycaemia?

Answer 40

Hyperglycaemia

Question 41

Does too little cortisol result in hyper or hypoglycaemia?

Answer 41

Hypoglycaemia

Question 42

What is the effect of cortisol on renal blood flow and GFR?

Answer 42

Increases renal blood flow + GFR

Question 43

What is the effect of cortisol on bone formation?

Answer 43

Inhibits bone formation

Question 44

Which term describes the body's physiological response to stress?

Answer 44

General adaptation syndrome

Question 45

What are the 3 phases of general adaptation syndrome?

Answer 45

Alarm reaction Resistance Exhaustion

Question 46

Which 3 ways can cortisol be measured?

Answer 46

Morning serum cortisol (Addison's) Late night salivary cortisol 24-hour urinary free cortisol Low-dose dexamethasone suppression test

Question 47

Why might Addison's disease cause salt cravings?

Answer 47

Addison's disease is an autoimmune condition targeting all areas of the adrenal gland. Low levels of aldosterone reduces sodium reabsorption