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203 - Theme 1 - The Endocrine System > L19 - Endocrine aspects of male hypogonadism > Flashcards

L19 - Endocrine aspects of male hypogonadism Flashcards

1
Q

Testosterone

A

Steroid hormones

Secreted both in men and women - testes, ovary and adrenal

Normal young men produce about 7mg each day, of which less than 5% is derived from adrenal secretions

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2
Q

How does testosterone travel in the blood?

A

Testosterone in blood is largely bound to plasma protein, with only about 2% present as free hormone

  • about half (>50%) is bound to albumin
  • 44% is bound to sex hormone-binding globulin (SHBG)
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3
Q

2 anatomical units of the testes

A

Seminiferous tubules in which inhibit B and anti-Mullerian hormone are synthesised by Sertoli cells and sperm are produced

An interstitium containing Leydig cells that produce androgens and peritubular myoid cells

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4
Q

Synthesis of androgens

A

Cholesterol is converted into pregnenolone using LH

Pregnenolone is converted into progesterone and DHEA

Both of these are converted into testosterone

Testosterone is broken down into DHT via 5A reductase and estradiol by aromatase from FSH

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5
Q

Testosterone: The HPA axis

A

Pulsatile secretion of GnRH

Secretion of LH and FSH

LH and FSH are composed of two glycoprotein chains

LH is involved in release of testosterone

FSH is involved in spermatogenesis and Inhibin B secretion

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6
Q

Testosterone: mechanism of action

A

Like other steroid hormones, testosterone penetrates the target cells whose growth and function it stimulates

Androgen target cells generally convert testosterone to 5 a-dihydrotestosterone before it binds to the androgen receptor

Alternatively, testosterone can be aromatised to oestrogens, which exert effects that are independent of, opposite to, or synergistic to this of androgen

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7
Q

Testosterone action

A

Regulation of gonadotrophin secretion by the hypothalamic pituitary system

Initiation and maintenance of spermatogenesis

Formation of the male phenotype during embryogenesis

Promotion of sexual maturation at puberty and its maintenance thereafter

Increase in lean body mass and decrease in fat mass

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8
Q

Hypogonadism: decrease in 2 major functions of the testes

A

1) Sperm production

2) Testosterone production

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9
Q

Definition of primary hypogonadism

A

Disease of the testes

Testosterone below normal and the serum LH/FSH are above normal

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10
Q

Definition of secondary hypogonadism

A

Disease of the hypothalamus or pituitary

Testosterone below normal and the serum LH/FSH are normal or low

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11
Q

Primary causes of hypogonadism

A

Klinefelter syndrome

Cryptorchidism

Infection-mump

Radiation

Trauma

Torsion

Idiopathic

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12
Q

Secondary causes of hypogonadism

A

Congenital GnRH deficiency

Hyperprolactinaemia

GnRH analog

Androgen

Opioids

Illness

Anorexia nervosa

Pituitary disorder

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13
Q

Clinical features of hypogonadism

A

First trimester - female genitalia to ambiguous genitallia to partial virilization

Third trimester - micropenis

Prepubertal - failure to undergo or complete puberty

Adults

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14
Q

Symptoms/signs of hypogonadism

A
  • Incomplete sexual development, eunuchoidism
  • Decreased sexual desire & activity
  • Decreased spontaneous erections
  • Breast discomfort, gynaecomastia
  • Decreased body hair (axillary and pubic)
  • Very small or shrinking testes (esp<5ml)
  • Inability to father children, low/zero sperm count
  • Decrease in height, low-trauma fracture, low BMD
  • Decrease in muscle bulk and strength
  • Hot flushes, sweats
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15
Q

Less specific symptoms/signs of hypogonadism

A

Decreased energy, motivation, initiative, aggressiveness, self-confidence

  • Feeling sad, depressed mood, dysthymia
  • Poor concentration and memory
  • Sleep disturbance, increased sleepiness
  • Mild anaemia - normochromic, normocytic, in the female range
  • Increased body fat, BMI
  • Decreased physical or work performance
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16
Q

Conditions with a High Prevalence of hypogonadism (Screening Suggested)

A

-Sellar mass, radiation to sella, other sellar disease
-On meds that affect T production or metabolism
=>Glucocorticoids, ketoconazole, opioids
-HIV-associated weight loss
-ESRD and maintenance hemodialysis
-Moderate to severe COPD
-Osteoporosis or low trauma fracture (esp if young)
-Type 2 diabetes mellitus
-Infertility

17
Q

Relevant Medical History

A
  • Puberty and sexual development
  • Past/present major illnesses
  • Past/present nutritional deficiency
  • All prescription and non-prescription drugs
  • Relationship problems
  • Sexual problems
  • Major life events
  • Related family history
  • Recent changes in body (breasts)
  • Testicle problems

Look out for recreational drug use, eating disorders and excessive exercise

18
Q

Examination of hypogonadism

A

-Amount of body hair
-Breast exam for enlargement/tenderness
-Size and consistency of testicles
-Size of the penis
-Signs of severe & prolonged hypogonadism
=>loss of body hair
=>reduced muscle bulk and strength
=>osteoporosis
=>smaller testicles
-Arm span

19
Q

Investigations for hypogonadism

A 
Serum testosterone
LH/FSH
SHBG
LFT
Semen analysis
Karoyotyping
Pituitary function testing
MRI
DEXA scan
20
Q

Guidelines on screening for hypogonadism

A

Initial screen = morning total testosterone

  • levels are highest in the morning
  • normal testosterone is generally age dependent

Confirmation = repeat morning total testosterone
-free or bioavailable

Do not screen during acute or subacute illness
-illness, malnutrition, and certain medications may temporarily lower testosterone

21
Q

What lowers SHBG?

A

-Moderate obesity
-Nephrotic syndrome
-Hypothyroidism
-Use of
=>glucocorticoids
=>progestins
=>androgenic steroids

22
Q

What raises SHBG?

A
  • Ageing
  • Hepatic cirrhosis
  • Hyperthyroidism
  • Anticonvulsants
  • Oestrogens
  • HIV infection
23
Q

Treatment for hypogonadism

A

Testosterone

  • gel
  • injection
  • buccal/patch/pellet
24
Q

Monitoring of hypogonadism

A

Testosterone

PSA

FBC

DRE

DEXA

25
Q

Contraindications to Testosterone Therapy

A 
Breast or prostate cancer
Lump/hardness on prostate exam by DRE
PSA >3 ng/ml that has not been evaluated for prostate cancer
Severe untreated BPH (AUA/IPSS >19)
Erythrocytosis (hematocrit >50%)
Hyperviscosity
Untreated obstructive sleep apnea
Severe heart failure (class III or IV)
26
Q

What is gynaecomastia?

A

A benign proliferation of the glandular tissue of the male breast

It may be unilateral or bilateral

27
Q

How is gynaecomastia diagnosed?

A

On exam as a palpable mass of tissue at least 0.5cm in diameter (usually underlying the nipple)

28
Q

Prevalence of gynaecomastia?

A

60% of boys during puberty - transient

30-70% in adult men

29
Q

Causes of gynaecomastia?

A
  • Persistent pubertal gynaecomastia
  • Drugs
  • Idiopathic
  • Cirrhosis or malnutrition
  • Hypogonadism
  • Testicular tumour
  • Hyperthyroidism
  • Chronic renal insufficiency - Leydig cell dysfunction
30
Q

History taking in gynaecomastia

A 
Duration
Breast pain/tenderness
Systemic disease
Weight gain or loss
Use of medication/recreational drugs
Exposure to chemicals
Fertility
Sexual function
Family history
31
Q

Examination of gynaecomastia

A
  • Virilisation
  • Testicular size
  • Penis
  • Sign of CLD or CRF
  • Thyroid
  • Breast
32
Q

Investigation of gynaecomastia

A
  • Testosterone
  • LH/FSH
  • Prolactin
  • LFT/U&Es
  • B-hCG
  • TFT
  • Oestrogen
  • U/S-mamogram
33
Q

Treatment of gynaecomastia

A

Conservative - reassurance

Treatment of cause

Tamoxifen

Surgery

203 - Theme 1 - The Endocrine System (11 decks)

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