Androgens & Anabolic Steroids Flashcards
Where are steroids hormones primarily secreted from?
- Testes
- Lesser amounts from adrenals (10% males)
Where is Testosterone generated in females and how much?
- Ovaries generate about half the circulating T
- Adrenals contribute to other half
- Initially as Androstenedione and DHEA - T levels in females are less than 10% of males
What is the principal androgen?
- Testosterone
8 mg/day, 0.5 ug/dL (males)
What is DHEA?
- Dehydroepiandrosterone
- Most abundant testosterone intermediate
- Much weaker androgenic properties
- Produced in Adrenals
What is Androstenedione?
- Last intermediate in T synthesis
- 2-3 mg/day from adrenals and testes/ovaries, 0.15 ug/dL.
- Levels vary greatly in females w/ menstrual cycle
What are the therapeutic uses of Androgens?
- Male Hypogonadism (T def.)
- Prepubertal/postpubertal - Male Senescence/Impotence
- May increase bone mass, libido, cause prostatic hypertrophy - Wasting states (AIDS) Anabolic needed
- Female Hypopituitarism/hypogonadism
- Androgens are necessary fro long-bone growth, some secondary sex charac. - Endometriosis
- Suppression of ovarian hormones (Danocrine) - Male anti-fertility? (still impotent)
- Enhancement of female libido?
What are the therapeutic uses of Anti-Androgens?
- Prostate Cancer
- Benign Prostatic Hypertrophy (BPH)
- Reverse impaired urinary flow - Female hirsutism
- Male pattern baldness (Propecia)
- Precocious Puberty
- Chemical Castration?
Why are Anti-Androgens used for Prostate Cancer?
- Prostatic cancer cells are initially androgen dependent.
What structures secrete testosterone?
- Leydig cells of testes
2. Corpus Luteum of ovary.
What is the rate limiting step in the synthesis of Testosterone?
- Conversion of Cholesterol to Pregnenolone by side chain cleavage.
What regulates Testosterone secretion?
- LH from pituitary
2. Binds a cell surface receptor to Increase cAMP.
What CYP converts Pregnenolone to DHEA?
- CYP17 (Steroid 17a-hydroxylase)
- Removes side chain leaving KETONE group
What is caused by a deficiency in CYP17?
- CAH and Female phenotypy, w/ inability to reach sexual maturity.
How is DHEA converted to Androstenedione and then to Testosterone?
- 3B-hydroxysteroid dehydrogenase
2. 17B-hydroxysteroid dehydrogenase (testes, ovaries)
What is special about 17 beta-hydroxysteroid dehydrogenase?
It is unique to the sex steroid synthesis pathway.
What is LH release in response to?
- Gonadotropin Releasing Hormone (GnRH)
How is GnRH secreted?
- By the Hypothalamus into the hypothalamohypophyseal portal system. (blood)
- Released in Pulsatile pattern
- 120 min frequency in males, 60-90 min frequency in females.
- LH (and FSH) release follows this pattern
- Constant GnRH levels inhibit LH release.
What type of variation do Testosterone levels exhibit?
- Diurnal and Pulsatile Variation.
- Levels are greatest in early morning and lowest in evening.
How does Testosterone inhibit LH and FSH release from pituitary?
2 Mechanisms
- Inhibition of GnRH release
- Down-regulation of GnRH receptors in pituitary.
How is Testosterone converted to dihydrotestosterone (DHT)?
By 5alpha-reductase.
gets rid of double bond in T
What is DHT and what does it do?
- Dihydrotestosterone
2. Binds the androgen receptor w/ 10 fold higher affinity and is believed to be the active form of Testosterone.
What is 5alpha-reductase type2?
- T –> DHT
2. found in external genitalia & T responsive tissues in men and women.
What happens in the absence of 5alpha-reductase?
- Results in female phenotype
- At puberty the sex organs in these pseudofemales may develop (appear) w/ surge in T.
- Deficient individuals will have normal to elevated T levels.
- Tissues that lack the reductase have minimal and primarily an ANABOLIC response to T (muscle)
What is 5alpha-reductase Type 1?
- Found in the Liver and some in Braine areas.
- NOT involved in Sexual Development
- 100-fold LOWER affinity for T.
What is Testosterone and DHT metabolized to and where?
- Androsterone, Etiocholanolone, androstandedione, and Androstanediol.
- Liver
How are metabolites of T excreted?
ALL metabolites are inactive and excreted in urine.
What is necessary for spermatogenesis?
- Testosterone
What cells secrete Androgen-Binding Protein (ABP)?
Sertoli Cells
-Retains Testosterone in seminiferous tubules.
What is the level of Testosterone in Testes compared to Serum?
- Level in testes 100x > serum.
What is circulating Testosterone bound to?
- Sex Hormone-Binding Globulin (SHBG)
2. Albumin.
Which is the higher affinity carrier, Albumin or SHBG?
- SHBG is the high affinity carrier.
- 98% of circulating T protein bound and unavailable for biological action.
- 40% to SHBG
- 60% to Albumin
What is the reputed male pheromone?
- Androstandienone
- Has a strong odor of sweat to most
- Lacks androgenic or anabolic effects
- Reported to positively affect mood of women, increase “caring feelings”
- Commonly used in male fragrances
- Selectively activates the vomeronasal organ in women - Not everyone can smell AND to some it smells like vanillin to some it smells like sweat/unpleasant.
What happened in the carefully controlled test of AND?
repeated sniffing of androstadienone maintained elevated levels of salivary Cortisol.
AND maintained better mood, higher sexual arousal, and physiological arousal.
Why do fetal testes secrete Testosterone?
- To stimulate development of internal and external male genitalia.
What drives T secretion in fetal testes?
- Human Chorionic Gonadotropin (hCG) early and fetal LH late.
- Deficiency or Insensitivity results in ambiguous or female genitalia.
- T levels fall to near zero after birth.
During puberty what happens to levels of Testosterone?
Rise to:
- 500-700 ng/dL (males)
- 30-50 ng/dl (females)
- Lack of androgens in either sex results in incomplete sexual maturation.
At what age do Testosterone levels gradually fall?
After age 30 in BOTH sexes.
- Not significant until after age 70, as metabolic clearance of T also decreases.
What happens to SHBG levels as age increases?
- Levels gradually INCREASE with age, contributing to lower FREE T levels.
What is the level of Free Testosterone in elderly men compared to young adults?
Elderly men have levels 40% of young adult.
-Contributes to decrease in Energy, Libido, Muscle Mass, and Strength.
What is shown to happen to Testosterone levels when men become fathers?
- T levels drop
- Biggest drop occurs in most devoted dads.
- Single men w/ higher T levels were more likely to find partners and become fathers.
What is the Biochemical definition of Testosterone Deficiency?
- Less than 300 ng/dL plasma T for men less than 40 yr.
- Less than 200 ng/dL for men 40-70 yr and 3 clinical signs
- Yields an incidence of TD of 6-12%.
In which people is Testosterone Deficiency most common?
- Obesity
- Diabetes (50% incidence in obese diabetic men)
- Hypertension
- Hyperlipidemias
What does a lower ratio of Testosterone to SHBG predict?
Poorer memory and cognitive status in men older than 50 years.
What are lower testosterone levels associated with?
Greater incidence of Cardiovascular disease in elderly men (>70yr)
1. > 550 ng/dL were protective in a second study of 2400 men >age 69
What are main signs and symptoms of T deficiency?
- Reduced Libido
- Erectile Dysfunction (ED)
- Reduced intensity of orgasm and sensation
- Osteoporosis or low BMD
- Decreased spontaneous erection
- Oligospermia or Azoospermia
- Very small or shrinking testes
- Hot flushes, sweats
- Breast discomfort, gynecomastia
- Loss of pubic and axillary hair, reduced shaving.
What are less specific signs and symptoms of T deficiency?
- Decreased energy, or vitality, increased fatigue
- Depressed mood
- Reduced muscle mass and strength
- Poor concentration and memory
- Sleep disturbance, increased sleepiness
- Mild anemia
- Increased body fat, body mass index
- Diminished physical or work performance.
What are the consequences of androgen deficiency in prepubertal males?
- Lack of sexual maturation: growth of genitals, pubic and axial hair, increase in muscle mass, deepening of voice.
- Elongated arm and leg bones, gynecomastia.
What are consequences of androgen deficiency in adult males?
- Loss of libido, energy, hematocrit, muscle mass and strength, bone density, sexual hair.