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Endocrinology BM > Gonads (2) 11 > Flashcards

Gonads (2) 11 Flashcards

1
Q

What is testosterone a precursor for?

A
  • 17b-oestradiol and oestrone

- dihydrotestosterone

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2
Q

What is the difference between dihydrotestosterone and its precursor?

A
  • it is far more potent but acts on the same androgen receptors
  • it is produced in the target tissue that has the 5alpha-reductase enzyme
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3
Q

Which tissues have the 5alpha-reductase enzyme?

A
  • prostate
  • testes
  • skin
  • brain
  • pituitary
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4
Q

How are oestrogens formed from the precursor?

A

Testosterone is aromatised by aromatase to form oestrone and 17b-oestradiol

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5
Q

What tissues is aromatase found in?

A
  • adrenals
  • testes
  • liver
  • skin
  • brain
  • adipose
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6
Q

How is testosterone and DHT transported in blood?

A
  • Sex hormone binding globulin (SHBG) = 60%
  • Albumin = 38%
  • Bioactive (free) = 2%
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7
Q

Where is the other testosterone transport?

A

Testosterone can be found in seminiferous fluid (semen) bound to Androgen binding globulin (ABG)

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8
Q

What are the actions of androgens on the foetus?

A
  • stimulate internal and external genitalia formation
  • stimulate general growth
  • affect behavioural characteristics
  • can be converted to oestrogens to bind to receptors in the brain for behavioural changes
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9
Q

What are the actions of androgens in adults?

A
  • SPERMATOGENESIS
  • growth/development of genitalia, secondary sex glands and secondary sex characteristics (beard/pubic hair)
  • stimulation of protein anabolism
  • Pubertal growth spurt (GH)
  • Behavioural (CNS) effects
  • Feedback regulation (to control LH/FSH)
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10
Q

Definition of oestrogens

A

Any substance (natural or synthetic) that induces mitosis in the endometrium

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11
Q

What is the main hormone in the menstrual cycle?

A

17b-oestradiol

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12
Q

What is the main hormone in pregnancy

A

Oestriol

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13
Q

What is the precursor to 17b-oestradiol and oestriol?

A

oestrone

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14
Q

What are the principal actions of oestrogens?

A
  • mitosis of endometrium
  • final maturation of follicle and stimulation of LH surge
  • effects on vagina and cervix (secretions)
  • Stimulates growth of breast ductile system
  • decreases sebaceous gland secretion
  • increased salt/water reabsorption
  • increased plasma protein sysnthesis
  • Metabolic actions on lipids e.g. increase HDL levels
  • stimulates osteoblasts
  • influences other hormones
  • behavioural effects
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15
Q

Progestogens Definition

A

Any substance (natural or synthetic) that induces secretory changes in the endometrium

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16
Q

What is the main Progestogen?

A

PROGESTERONE

-17hydroxyprogesterone

17
Q

What are the principal actions of progestogens?

A
  • stimulate secretory activity in the endometrium and cervix
  • stimulate growth of breast alveolar system
  • decrease renal Na+/Cl- reabsorption
  • associated with increase in body temperature
  • -ve feedback for GnRH
18
Q

What is the steroid hormone mechanism of action?

A

Have a genomic effect via intracellular receptors. The receptor-hormone complex acts as a transcription factor. May act on G-protein like receptors to not have a genomic effects

19
Q

Describe major points in the hypothalamo-pituitary-testes axis.

A

1) hypothalamus produces GnRH
2) GnRH causes LH and FSH production in the pituitary
3) LH acts on Leydig cells to produce testosterone
4) testosterone has a -ve feedback on LH and GnRH production
5) FSH acts on sertoli cells to produce Inhibin
6) Inhibin has a -ve feedback to reduce FSH, LH and GnRH

20
Q

Give an example of auto-positive feedback

A

oestrogens produced by a granulosa cell with bind to Oestrogen receptors on the same cell and produce more oestrogens having activated the aromatase enzyme by a secondary messenger. Therefore, granulosa cells multiply and get bigger and plasma oestrogen levels increase

21
Q

What hormone does the graffarian follicle produce?

A

17b-oestradiol

22
Q

What is Amenorrhoea

A

Absence of menstrual cycles

Primary = never happened
Secondary = did but stopped
23
Q

What is Oligomenorrhoea

A

Infrequent menstrual cycles (less than every 6-8 weeks)

24
Q

What is infertility?

A

Inability to get pregnant following 12 months of regular unprotected sex

25
Q

What are the causes of infertility?

A
  • pituitary failure (e.g.tumour)
  • prolactinoma (excess prolactin with galactoria symptom)
  • testicular failure
  • ovarian failure

Polycystic Ovarian Syndrome (infrequent periods/hyper-androgenaemia/ polycystic ovaries)

Endocrinology BM (12 decks)

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