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Gonadal Function Flashcards

1
Q

What is the function of the gonads?

A

Steroid (Sex) Hormone production

  • Predominantly Oestrogens in women
  • Predominantly Androgens in men

Maturation of the germ cells

  • Ova in women
  • Sperm in men
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2
Q

Describe the features of GnRH

A
  • Pulsatile release
  • Stimulates LH & FSH release from pituitary gonadotrophes
  • Regulated by circulating gonadal steroids (Testosterone, 17ß-oestradiol)
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3
Q

What is the function of FSH?

A

Stimulates

  • spermatogenesis in male
  • ovarian oestrogen secretion in female
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4
Q

What is the function of LH?

A

Testosterone secretion by the Leydig cells in men

Stimulates ovulation in the female

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5
Q

What is the function of the Hypothalamic-Pituitary-Gonadal-Axis?

A

It controls hormone release, that then controls the ovaries and testes

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6
Q

How does testosterone circulate?

A

Circulates as free (2%) and bound to sex hormone
binding globulin (60%), albumin (38%) and other
proteins (<1%)

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7
Q

When are testosterone levels highest?

A

Morning

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8
Q

What are the functions of testosterone?

A
  • Spermatogenesis
  • Secondary sexual characteristics
  • Pubic and axillary hair
  • Musculoskeletal development
  • Libido
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9
Q

How is testosterone metabolised?

A

Metabolised by 5α-reductase to produce dihydrotestosterone

OR

Metabolised by aromatase to produce oestrodiol

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10
Q

What is the function of Sex Hormone Binding Globulin?

A

Blood transport protein for testosterone. Testosterone bound SHBG is not biologically active
• Reversible binding

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11
Q

What is the result of excess increase in SHBG?

A

Hypogonadism
Oestrogen
Hyperthyroidism
Liver cirrhosis

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12
Q

What is the result of excess decrease in SHBG?

A 
Hypothyroidism
Obesity
Diabetes
Glucocorticoid
Nephrotic syndrome
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13
Q

What are the features of hypogonadism in men?

A

Defective spermatogenesis or testosterone production or both

Can be primary or secondary

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14
Q

What are the features of Primary Hypogonadism in men?

A

Testicular failure due to primary testicular disease
Serum testosterone ↓, FSH and LH ↑

Congenital - Klinefelter’s syndrome, testicular agenesis, 5 α- reductase, Haemochromatosis and other enzyme defects

Acquired - bilateral orchitis, irradiation, cytotoxic drugs,
bilateral varicocele

Treat the cause, Testosterone replacement

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15
Q

What are the features of Secondary Hypogonadism in men?

A

Testicular failure secondary to hypothalmic-pituitary
disease
Serum testosterone ↓ , FSH and LH normal or ↓

Pituitary disorders – tumours, panhypopituitarism
Hypothalamic disorders - Kallman’s syndrome

Treat the cause, Testosterone replacement, GnRH for fertility

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16
Q

How can Spermatogenesis be detected?

A

Semen analysis (NICE)
At least 2 samples should be assessed in the same
laboratory
Collection by masturbation at temp (15C to 38C) and
delivered quickly to the laboratory

FSH: FSH correlates with sperm count
- Obstructive azoospermia - Normal FSH
• Inhibin B: Low IB indicates Sertoli cell failure
• AMH: Low AMH indicates Sertoli cell failure

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17
Q

What tests can be performed to determine cause of problems with male fertility?

A 
Semen Analysis
Patient History
Physical Exam
Testosterone levels in morning
LH and FSH levels

Medication and chronic illness need to be considered

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18
Q

What is the cause of excess prolactin in men?

A

Increased levels of prolactin in males can be caused by a pituitary tumour (MRI needed to confirm)

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19
Q

What is Gynaecomastia?

A

Breast development in men

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20
Q

What is the cause of Gynaecomastia?

A

 Disturbance of the balance of oestrogen to androgens

Can be due to:

  • Physiological causes
  • Pharmacological causes
  • Pathological causes
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21
Q

What are the pharmacological causes of Gynaecomastia?

A 
Oestrogen
Digoxins (binds to oestrogen receptors)
Cytotoxics (testicular damage)
Antiandrogens (spironolactone, cyproterone)
Others- methyldopa, phenothiazines, etc.
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22
Q

What are the pathological causes of Gynaecomastia?

A

Increased oestrogens
- Chronic liver disease, established renal failure, Cushing’s syndrome, hyperthyroidism, tumors.

Decreased androgens
- Klinefelter’s syndrome

Androgen insensitivity
- Testicular feminization, refeeding after starvation

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23
Q

What is the function of oestrodiol?

A

Development of female sex organs and secondary sex
characteristics

Menstruation

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24
Q

When is oestrodiol normally low?

A

Very low levels in prepubertal girls

Decreases following the menopause

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25
Where is Inhibin A produced?
Made by the dominant follicle and corpus luteum.
26
What is the function of Inhibin A?
Endocrine function, Suppresses FSH
27
When are increases in Inhibin A normally seen?
Rises in late follicular phase and maximal in luteal phase. Thought that negative control of FSH in luteal phase shifts from E2 to IA. Increases during pregnancy, from the foetoplacental unit. Very high levels are seen at end of pregnancy
28
When is increase in Inhibin A seen in pathology?
Tumour marker for ovarian cancer
29
When can low Inhibin B be seen?
Ovarian failure
30
When can high Inhibin B be seen normally?
Raised IB may detect successful IVF treatment Women with IB (>45pg/ml) are 6.8 times more likely to conceive irrespective of age and day 3 FSH
31
When is high Inhibin B a pathological marker?
Raised in Polycystic Ovary Syndrome (marker for hyperstimulation?) Tumour marker for ovarian cancer
32
When is progesterone secreted?
Secreted by the corpus luteum during the luteal phase of the menstrual cycle and by the placenta in pregnancy
33
What is the function of progesterone?
Prepares the endometrium of the uterus to receive a fertilised ovum, maintains early pregnancy.
34
What is a marker of ovulation?
Day 21 Progesterone >30nmol/L indicative of ovulation in a 28 day menstrual cycle
35
What are the features of Anti-Mullerian Hormone (AMH)?
* Very low pre-puberty * Increased ovarian (antral follicles) production at puberty * Steadily decline over their reproductive years * Undetectable after menopause * Unaffected by menstrual cycle
36
How can detection of AMH be used clinically?
* Useful in detecting ovarian reserve * Best single marker to predict response to gonadotrophin stimulation * Predicts likelihood of conception in IVF * Tumour marker for granulosa cell cancers * Increased in PCOS
37
What are the features of ovarian androgens?
* Androstenedione is the main ovarian androgen. * Androstenedione is converted to oestrone and testosterone in extra-ovarian tissue. * Small amount of testosterone is secreted directly by the ovaries * Assay differences in testosterone
38
What is the Free Androgen Index (FAI)?
Free Androgen Index or FAI is a ratio used to determine abnormal androgen status in humans. • FAI = (Total Testosterone (nmol/L) x 100) / SHBG (nmol/L) Only applicable to women because the binding capacity of SHBG for Testosterone is large because of their relatively low testosterone and high SHBG concentrations
39
How is ovarian reserve tested for?
* Day 3 FSH: > 10 IU/L correlates with poor IVF success * AMH is the best single marker to predict response to gonadotrophin stimulation * Antral Follicular Count (AFC) uses ultrasound in early follicular phase: Low AFC correlate with poor IVF success Others – not recommended • Clomiphene stimulation test • Inhibin B: Women with IB (>45pg/ml) are 6.8 times more likely to conceive even when age and day 3 FSH are accounted for
40
What are the symptoms of ovarian dysfunction?
Presents with any or all of the following - Amenorrhoea/Oligomenorrhoea - Hirsutism with or without Virilism - Infertility
41
What are the most common causes of Amenorrhoea?
Pregnancy | Menopause
42
What is Oligomenorrhoea?
Infrequent menstrual cycles
43
What is Menorrhagia?
Abnormally heavy menstrual bleeding
44
What is Amenorrhoea?
Lack of periods - Primary- never menstruated >15years - Secondary- absence of menstruation for (3-) 6 months in a woman with previous menses
45
What are the features of Hypogonadotrophic hypogonadism in women?
Characterised by Low FSH, LH & E2 Hypothalamic-pituitary disorders may present with primary or secondary amenorrhoea depending on onset of illness before or after puberty Organic hypothalamic-pituitary disorders may be associated with other features of pituitary failure
46
What can cause organic hypothalamic-pituitary disorders?
As part of hypopituitarism - Hypothalamic and Pituitary tumours - Other Pituitary disease - Head trauma Without hypopituitarism - Isolated hyperprolactinaemia - Kallmann syndrome (Only 1o amenorrhoea) - Isolated gonadotrophin deficiency (only primary amenorrhoea)
47
What can cause functional hypothalamic-pituitary disorders?
Chronic systemic disease Malnutrition/ Anorexia Nervosa Exercise induced
48
What are the diagnostic features of primary ovarian failure?
High FSH & LH & Low E2 ( Low IA, IB & AMH)
49
What can cause primary ovarian failure?
Primary Ovarian failure with Primary Amenorrhoea (most common) - • Genetic Causes e.g. Turners Syndrome • Disorders of sexual differentiation Primary Ovarian failure with Secondary Amenorrhoea (Premature menopause) • Idopathic • Autoimmune • Physical insults – e.g. chemotherapy
50
What are the features of Polycystic Ovarian Syndrome (PCOS)?
Presents with Triad of: • Hyperandrogenism • Ovulatory dysfunction • Polycystic ovaries Associated with: • Obesity • Metabolic syndrome • Increased risk of uterine cancer
51
How does Hyperandrogenism present?
Clinically: Hirsuitism, acne, cliteromegaly Biochemically: - Increased Androgens (Testosterone, DHAS Androstenedione) - Low SHBG (Increased FAI) - (Increase LH:FSH ratio; Hyperprolactinaemia)
52
How does Ovulatory dysfunction present?
Oligomenorrhea/Amenorrhoea
53
How are polycystic ovaries diagnosed?
Ultrasound: 1. 12 or more follicles measuring 2-9 mm in diameter or 2. Increased ovarian volume (> 10 cm3)
54
What is the menopause?
The menopause is defined as the twelve months after a woman’s final menstrual period. It marks the end cyclic ovarian function and ovulation and thus reproductive capabilities
55
Describe the continuum of the menopause
Pre-menopause Menopausal transition (Peri-menopause) Post-menopause
56
Describe the biochemical progress of the menopause
Initial event is a decline in Inhibin B in early follicular phase, when cycle irregularity is first observed. In late menopause transition insufficient E2 produced by reduced number of ovarian follicles to induce endometrial proliferation and subsequent bleeding also a fall in Inhibin A. Decline in Inhibin A and E2 loss of -ve feedback on gonadotrophins results in elevated FSH and LH
57
How can menopause transition be detected?
* FSH best marker: LH increase is later and less consistent than FSH. * LH>FSH (and E2 > 180pmol/L) indicate presence of viable oocytes or midcycle * E2 declines but secretion remains cyclical. * Results may be masked by Oral Contraceptive Pill (OCP) – repeat after stopping OCP for 6-8 weeks However, in women 45-55 yr with • Irregular cycles, 80% have FSH >15 U/L • Regular cycles, 45% have raised FSH >15 U/L i.e “Normal FSH” does not exclude perimenopause • FSH >15 U/L does not preclude possibility of ovulatory cycles i.e potentially fertile
58
What are the features of the post-menopause period?
* Increased FSH * Increased LH * Low E2 * (Low IA & IB) FSH and LH fall in old age Major post-menopausal oestrogen is oestrone - produced from peripheral conversion of androstenedione. oestrone has 20% cross reactivity with some E2 assay.
59
What are the symptoms of menopause?
• Vasomotor symptoms - Hot Flushes • Insomnia • Genital atrophy, Vulvovaginal dryness, • Sexual dysfunction, Dyspareunia • Depression, Anxiety, Labile mood, Fatigue Poor memory, Headache • Dry skin, Thinning scalp hair, Hirsutism Increased Risk of Osteoporosis, Cardiovascular Disease, Alzheimers
60
What causes the symptoms of menopause?
Primarily related to oestrogen deficiency
61
How can the symptoms of menopause be treated?
Hormone Replacement Therapy • Short term benefit for vasomotor symptoms Some women are more suitable for HRT than others, however there are complications associated with HRT
62
What complications are associated with HRT?
``` Oestrogen and Progestin (Per 10,000 women, per annum) 7 more CHD Events 8 more strokes 8 more invasive breast cancers 18 more VTEs 8 more PEs 6 fewer colorectal cancer 5 fewer hip fractures ``` ``` Oestrogen Alone (Hysterectomy) (Per 10,000 women, per annum) 5 fewer CHD events 12 more strokes 7 fewer breast cancers 7 more VTE 3 more PEs 1 more colorectal cancer 6 fewer hip fractures ```

Clinical Immunology and Biochemistry (14 decks)

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