30 - Steroid Hormones

Question 1

Steroid hormones

Answer 1

o Steroids are a class of lipid derived from cholesterol
o Cholesterol is converted into steroid hormones in sterogenic endocrine cells (adrenal and gonads)

Question 2

What do steroid hormones include?

Answer 2

o Cortisol and aldosterone, made in the adrenal cortex
o Testosterone, made by the testis
o Progesterone and oestradiol, made in the ovary

Question 3

What do steroid hormones affect?

Answer 3

o Carbohydrate metabolism
o Salt and water balance reproductive function

Question 4

What does synthesis of steroid hormones require?

Answer 4

Synthesis of steroid hormones from cholesterol requires modifications that occur to the basic ring structure

Question 5

Structure of steroids that is altered

Answer 5

The ring structure itself isn’t altered, rather the side chains can be altered
o In the case of progesterone, glucocorticoids, and mineralocorticoids, the side chain is split giving a 21-carbon compound
o In the case of androgens, it is split to give a 19-carbon compound
o In oestrogen it gives a C18 compound

Question 6

Where does the synthesis of steroid hormones take place?

Answer 6

The synthesis of steroid hormones takes place in the adrenal gland and we have 2 adrenal glands, each located above one kidney

Question 7

Adrenal gland divided into how many zones?

Answer 7

Adrenal hormones, epinephrine and norepinephrine, are synthesised in the adrenal medulla, whereas the adrenal steroid hormones are synthesised in the adrenal cortex

Question 8

Adrenal cortex zones

Answer 8

The adrenal cortex is further subdivided into three zones:
o The inner zone (zona reticularis) which is next to the adrenal medulla
o The zona fasciculata
o The outer zone (zona glomerulosa)

Surrounding all of these zones is connective tissue to protect the organ

Question 9

What are in each of the individual zones?

Answer 9

In each of the individual zones there are enzymes that synthesise particular classes of steroids

Question 10

What is the first conversion of the synthesis of a steroid hormone?

Answer 10

Whenever we are synthesising a steroid hormone, the first conversion is always cholesterol to pregnenolone, and this takes place in the mitochondria

Question 11

Zona glomerulosa

Answer 11

o The enzymes which can covert cholesterol to aldosterone
- Aldosterone acts on the glomeruli of the kidney
o Aldosterone is the principal mineralocorticoid

Question 12

Zona fasciculate and zona reticularis

Answer 12

o Have the enzymes to synthesise a group of corticoids and small amounts of androgens
o Androgens are produced massively in the testes of males, but both male and females produce small numbers of androgens

Question 13

Zona fasciculata

Answer 13

• Cholesterol is converted to glucocorticoids of which the principal one Is cortisol
• There is also corticosterone which is an anti-inflammatory drug
• The enzymes are present for the conversions

Question 14

Zona reticularis

Answer 14

The initial conversion of cholesterol to pregnenolone doesn’t take place in the zona reticularis
o Intermediatory metabolisms, including 17 hydroxyprogesterone and 17 hydroxy pregnenolone is transported into the zona reticularis for further conversion to the androgens