30 - Steroid Hormones Flashcards

1
Q

Steroid hormones

A

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

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2
Q

What do steroid hormones include?

A

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

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3
Q

What do steroid hormones affect?

A

o Carbohydrate metabolism
o Salt and water balance reproductive function

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4
Q

What does synthesis of steroid hormones require?

A

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

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5
Q

Structure of steroids that is altered

A

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

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6
Q

Where does the synthesis of steroid hormones take place?

A

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

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7
Q

Adrenal gland divided into how many zones?

A

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

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8
Q

Adrenal cortex zones

A

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

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9
Q

What are in each of the individual zones?

A

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

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10
Q

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

A

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

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11
Q

Zona glomerulosa

A

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

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12
Q

Zona fasciculate and zona reticularis

A

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

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13
Q

Zona fasciculata

A
  • 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
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14
Q

Zona reticularis

A

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

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