Steroid Hormones & thyroid function

Question 1

name of the process that makes T1 & T2 & describe it. & where process is done

Answer 1

a) Organification of thyroglobulin: bind oxidised I2 to thyroblobulin
b) Thyrosine + I2 (TPO*) => T1
T1 + I2 (TPO) => T2
*TPO= Thyroid peroxidase (oxidise)
c) follicle cells

Question 2

name of the process that makes T3 & T4 & describe it. & where process is done

Answer 2

a) Coupling of iodotryrosine
b) T1 + T2 => T3
T2 + T1 => rT3
T2 + T2 => T4
c) Thyroglobulin / colloid region

Question 3

Hashimoto disease has autoimmune Ab that target _

Answer 3

TPO (anti-TPO Ab => hypothyroidism)

Question 4

Which of the following thyroid hormones has the highest biological activity?

Answer 4

T3 (tri-iodothyronine)

* Note: bc T4 converted to active form by de-iodase = T3

Question 5

Which of the following thyroid hormones is more abundant?

Answer 5

T4 (tetra-iodothyronine aka thyroxine)

Question 6

4 phases of T3/T4 synthesis

Answer 6

1. Trapping of iodine
2. Adding Iodine to tyrosine (via organification w/ TPO)
3. Coupling of 2 iodonated tyrosine residues
4. lysosomes digest thyroglobulin and release T3 & T4

Question 7

What is iodine trapping?

Answer 7

• TSH strongly regulates iodine trapping

- Symport mechanism: 2Na+ & I2 (-ve) go in follicle cell from plasma

Question 8

Regulation of thyroid hormones is based on

Answer 8

Free T4 and free T3

Question 9

What is TBG? & significance if inc. or dec.

Answer 9

a) thyroxine-binding globulin: binds to thyroid hormones in circulation
b) inc. TBG = early liver disease
c) dec. TBG = late liver disease

Question 10

the effect of T3 on target cells

Answer 10

1. T3 diffuses to the nucleus
2. binds to thyroid receptor hormone
3. hormone-receptor complex binds to thyroid response element
4. initiate transcription & translation

Question 11

Describe the negative Fb loop for T3 & T4

Answer 11

1. TRH: thyrotrophin releasing hormone produced by hypothalamus
2. TSH produced by Ant. PT gland
3. Thyroid gland produce T3* & T4
4. Inc. T3 & T4 inhibits production of TRH & TSH

Question 12

difference b/w 1º & 2º disease & e.g of each

Answer 12

1º: disease in same organ (e.g. in thyroid gland)

2º disease in another organ => affects that organ (e.g. in hypothalamus/PT gland)

Question 13

Describe Grave’s disease (aka _) (include blood test expectations)

Answer 13

a) hyperthyroidism
- caused by Thyroid Stimulating Ig (TSI) Ab or anti-TSH receptor => similar effect to TSH => excess production of T3 & T4 by thyroid gland
- blood test show: elevated T3 & T4 & Low TSH (-ve Fb)

Question 14

Describe Hashimoto’s disease (aka _) (include blood test expectations)

Answer 14

a) hypothyroidism
- caused by TPO autoAb => dec. production of T3 & T4
b) blood test show: Low T3 & T4 & High TSH

Question 15

trophic hormone

Answer 15

a hormone which stimuates another organ to release a hormone

Question 16

Steroid hormone structure & 4-5 e.g.

Answer 16

a) 3x 6C + 1x 5C rings
b) - Sex steroids (androgens, testosterone)
- Progestogens (Progesterone)
- Glucocorticoids (Cortisol)
- Mineralcorticoids (aldosterone)
- Vitamin D (based on its structure)

Question 17

Most abundand steroid hormone & starting compound for synthesis of all steroid hormones is

Answer 17

pregnenolone

Question 18

What dictates whether a tissue responds to steroid hormones or not? & e.g. (2)

Answer 18

• Hormone receptors: FSH/LH/ACTH
• Enzyme profile: 18-hydrolase required for aldosterone synthesis - found in zona glomerulosa cells (outer zone) of adrenal cortex

Question 19

steroid hormones for male sexual development

Answer 19

• Androgens
• Didehydroepiandrosterone
• Testosterone

Question 20

steroid hormones for female sexual development

Answer 20

• Oestrogens
• Progesterone (maintain prego)
• Estradiol

Question 21

Give an e.g. for each group: (a) Glucocorticoid & (b) mineral corticoid

Answer 21

a) cortisol

b) aldosterone

Question 22

inc. cortisol = [inc./dec.] weight

Answer 22

inc

Question 23

According to circadian release of cortisol, cortsol is [Hi/lo} early in the morning & [Hi/Lo] @ night

Answer 23

a. Hi

b. Lo

Question 24

Hormonal regulation of cortisol

Answer 24

1. injury, fear stress => Corticotrophin Releasing Hormone (CRH) in hypothalamus
2. => Adrenocorticotropic hormone (ACTH) in Ant. PG
3. => Cortisol in adrenal cortex
4. Inc. [Cortisol] => -ve Fb => dec. CRH & ACTH

Question 25

Steroid-receptor complexes [location in cell] aggregate into (a) and are said to be (b)

Answer 25

inside cell

a) Homodimers
b) Activated

Question 26

2 Roles of heat shock proteins

Answer 26

Bind to unoccupied receptors to:

• keep receptor conformation in shape
• Prevent unoccupied recptors from binding to DNA

Question 27

The Activated receptor homodimers hormone bind to the (a), which in turn bind to both the TATA binding protein and the (b) to synthesise a new protein.

Answer 27

a) Co-activators

b) RNA polymerase

Question 28

Oxidation of iodide ions, I-, to nascent iodine, I0, or I3- is promoted by

Answer 28

TPO= Thyroid peroxidase

Question 29

What’s the most abundant circulating steroid hormone in humans?

Answer 29

didehydroepiandrosterone (DHEAS)

Question 30

Basal metabolic rate measures

Answer 30

number of kilojoules your body will burn on any given day, without taking into account any exercise you may do.

Question 31

The front line tests for diagnosis is measurement of serum thyroid hormone levels

Answer 31

• TSH & T4
• TSH & T3
• TRH & T4
• TRH & T3