Lecture 60

Question 1

What is a hormone?

Answer 1

1) A hormone is a chemical messenger that is synthesized and secreted by specialized cells in response to an external signal
2) For the most part, hormones are synthesized in one tissue and effect another

Question 2

What are 4 major steroid hormones?

Answer 2

1) Cortisol
2) Aldosterone
3) Estradiol
4) Testosterone

Question 3

What are characteristics of cortisol?

Answer 3

1) Synthesized in the adrenal glands
2) 21 Carbons
3) Affects the liver
4) Increases gluconeogenesis (gluconeogenic enzymes)

Question 4

What are characteristics of aldosterone?

Answer 4

1) Synthesized in adrenal glands
2) 21 Carbons
3) Affects the kidney
4) Increases Na+ reabsorption & increases K+ excretion

Question 5

What are characteristics of estradiol?

Answer 5

1) Synthesized in ovary (also small amounts in adrenal glands)
2) 18 Carbons
3) Affects the Uterus
4) Increases uterine mass

Question 6

What are characteristics of testosterone?

Answer 6

1) Synthesized in the testes (small amounts in the adrenal glands)
2) 19 Carbons
3) Affects muscle
4) Increases muscle mass

Question 7

What is the structure of a general steroid hormone?

Answer 7

1) 4 ring structure, with each ring labeled A, B, C, or D

2) Carbons 20 and 21 are branched off of carbon 17

Question 8

What is the structure of cortisol?

Answer 8

1) 21 hydroxylase
2) 17 hydroxylase
3) 11 hydroxylase

Question 9

What are the hydroxyl groups in cortisol important for its function?

Answer 9

Hydroxyl groups are important for the gluconeogenic activity of cortisol

Question 10

What is the structure of aldosterone?

Answer 10

1) 21 hydroxylase
2) 18 hydroxylase
3) 11 hydroxylase

Question 11

What is the same in the structures of estradiol & testosterone?

Answer 11

17 hydroxylase

Question 12

What is different in the structures of estradiol & testosterone?

Answer 12

1) Estradiol contains a phenolic A ring

2) Testosterone contains an A ring with a double bond between carbons 4 & 5

Question 13

Describe the pathway by which cortisol is produced

Answer 13

1) Stress induces the hypothalamus to produces corticotropic releasing factor (CRF)
2) CRF induces the pituitary gland to release Adrenocorticotropic Hormone (ACTH)
3) ACTH induces the adrenal glands to produce cortisol

Question 14

How is the cortisol production pathway regulated?

Answer 14

Cortisol autoregulates its own production pathway when it is present in high levels by inhibiting corticotropic releasing factor (CRF) & Adrenocorticotropic hormone (ACTH)

Question 15

What is the same between ACTH and Melanocyte Stimulating Hormone (MSH)?

Answer 15

Both hormones contain an identical first 13 amino acids

Question 16

What occurs in adrenal insufficiency?

Answer 16

Elevated levels of ACTH cause binding to MSH receptor and causes skin darkening

Question 17

What is Addison’s disease?

Answer 17

1) Addison’s disease is a disorder that occurs when your body produces insufficient amounts of certain hormones produced by your adrenal glands
2) In Addison’s disease, your adrenal glands produce too little cortisol and often insufficient levels of aldosterone as well
3) It is usually first observed in the oral cavity

Question 18

What is the function of desmolase?

Answer 18

1) A desmolase enzyme is one that catalyzes the formation or destruction of carbon-carbon bonds within a molecule
2) Splits side chains of cholesterol
3) Allows you to add hydroxyl groups
4) 21, 17, 11, 18 hydroxylase

Question 19

What are three characteristics of steroids?

Answer 19

1) Derived from cholesterol
2) Similar in strucure
3) Effective at very small concentrations (10^-8M)

Question 20

What are two functions of ACTH?

Answer 20

1) Allows cholesterol to be released from adrenal storage

2) Activates desmolase

Question 21

How are water insoluble cholesterols transported through the blood?

Answer 21

1) Steroid hormones bound by certain plasma proteins
2) Cortisol is bound by CBG (Cortisol binding globulin)
3) Estradiol + Testosterone are bound by sex hormone binding globulin (SHBG)
4) Aldosterone is bound by Aldosterone Binding Globulin (ABG)

Question 22

What mediates the specificity of steroid hormones?

Answer 22

1) Specificity is due to the presence of high affinity intracellular receptors that are specific for the specific hormone
2) Hormones travel to all cells, but only activate those with these intracellular receptors
3) Activated receptor is transported to the nucleus to affect transcription
4) Hormones contain DNA binding domains with zinc fingers that bind to hormone response elements

Question 23

How can cofactors assist hormone receptors?

Answer 23

1) They can either be coactivators or corepressors
2) A number of coactivators are histone acetyl transferases
a) Histone acetyl transferases cause histone acetylation so that histones bind less tightly to DNA, allowing looser DNA & more transcription (affect RNA Pol 2)

Question 24

How was steroid hormone action mediated in breast cancer trials?

Answer 24

1) Rats were given breast cancer with the use of DMBA & removal of ovaries (ovariectimized)
2) Only worked in 30% of women
3) Women respond to endocrine ablative therapy if they have breast cancer and are estrogen receptor positive (ER+)
4) Tamoxifen is an antiestrogen (blocks estrogen receptors)
5) Can also use aromitase inhibitor to prevent formation of estradiol from testosterone?