Endocrinology Part 4 - Gonadal Hormones Flashcards
ovarian hormone synthesis
Ovarian Steroidogenesis
testicular hormone synthesis
Testicular Steroidogenesis
enzyme that converts cholesterol to pregnenolone
cholesterol side-chain cleavage enzyme
enzyme that converts pregnenolone to progesterone
3-beta-hydroxysteroid dehydrogenase
enzyme that converts progesterone to 17-OH progesterone
17-a-hydroxylase
enzyme that converts pregnenolone to 17-OH-pregnenolone
17-a-hydroxylase
enzyme that converts 17-OH-pregnenolone to 17-OH-progesterone
3-beta-hydroxysteroid dehydrogenase
enzyme that converts DHEA to androstenedione
3-beta-hydroxysteroid dehydrogenase
enzyme that converts 17-OH-pregnenolone to DHEA
17,20-Lyase
enzyme that converts 17-OH-progesterone to androstenedione
17,20-Lyase
enzyme that converts DHEA-S to DHEA
sulfotransferase
enzyme that converts androstenedione to testosterone
17-beta-hydroxysteroid dehydrogenase
enzyme that converts testosterone to dihydrotestosterone
5-a-reductase
where does conversion of testosterone → estradiol and androstenedione → estrone takes place?
Ovaries
Peripheral tissues (aside from testes & ovaries)
females have testosterone due to this presence
DHEA
events that occur in peripheral tissues during ovarian/testicular steroidogenesis
- testosterone → (reduced) → dihydrotestosterone
- adrenal androgen (DHEA) → testosterone
- estriol (type of estrogen) → (hydroxylated) →estradiol
- testosterone → estradiol
- androstenedione → estrone
More potent than testosterone
Dihydrotestosterone
Responsible for masculinization of external genitalia (male gonads)
Dihydrotestosterone
What occurs when ↑ dihydrotestosterone in female
masculinization of female external genitalia
percentage of protein bound sex hormones
98-99%
cannot fuse to the vascular system → cannot interact with the target cells
percentage of free/unbound sex hormones
1-2%
biologically active
TRANSPORT PROTEINS OF GONADAL HORMONES
Sex Hormone-Binding Globulin (SHBG)
Corticosteroid-Binding Globulin (CBG)
Albumin
Transports androgens and estrogens
Sex Hormone-Binding Globulin (SHBG)
Binds adrenal cortex hormones
Corticosteroid-Binding Globulin
Delivers progesterone & glucocorticoids (cortisol)
Corticosteroid-Binding Globulin
Principal androgen hormone in the blood
TESTOSTERONE
Most potent androgen among male
TESTOSTERONE
T/F
testosterone is only found in men
F
Testosterone → estrogen among female
95% of testosterone are synthesized by
Leydig cells of testis
5% of testosterone are synthesized by
Conversion of DHEA → testosterone
Controlled primarily by the 2 stimulating hormone produced by pituitary gland such as FSH and LH
TESTOSTERONE
2 stimulating hormone produced by pituitary gland that controls testosterone production
FSH
LH
stimulating hormone that acts on the germinal stem cells of male
FSH (Follicle-stimulating hormone)
stimulating hormone that acts on the Leydig cells of male (stimulate cholesterol conversion to testosterone)
LH (luteinizing hormone)
T/F
Amount of testosterone is affected by some physiologic factors
T
Circadian rhythm, Obesity, Age
physiologic factors that affects testosterone amount
Circadian rhythm
Obesity
Age
Peak of testosterone levels are seen during
8 am (after waking up)
Lowest testosterone levels are seen during
8 pm
plasma testosterone of obese individuals
decreased
how does age affect testosterone production
gradual testosterone ↓ after 30 y/o = 110 ng/dL/decade ↓
For growth & development of male reproductive system
testosterone
Reference value of testosterone
3.9–7.9 ng/mL (serum)
Transport Protein of testosterone (w/ %)
Albumin (50%)
Sex Hormone-Binding Globulin (45%)
T/F
Transport protein measurement in male is essential
because binding proteins conc. can determine
testosterone level
T
↑ SHBG = ↑ testosterone
T/F
Free testosterone level can be measured in lab
F
Conditions under Hypergonadotropic Hypogonadism (Testosterone)
Klinefelter’s Syndrome (XXY)
5-reductase Deficiency
Myotonic Dystrophy
Sertoli cell-only deficiency/germ cell aplasia
Testicular Injury and Infection (mumps orchitis)
Testicular Feminization Syndrome
What type of hypogonadism is Hypergonadotropic Hypogonadism (Testosterone)
Primary hypogonadism
Hormone levels in Hypergonadotropic Hypogonadism (testosterone)
Low testosterone (stimulates FSH/LH production)
Elevated FSH/LH
Condition with Impaired sperm production → infertility/sterility
Hypergonadotropic Hypogonadism (testosterone)
Male individual with 3 sex chromosomes
Klinefelter’s Syndrome (XXY)
Presence of XX (female chromosomes) in males
Klinefelter’s Syndrome (XXY)
Normal 23rd pair of chromosomes in male
XY
Manifestations of Klinefelter’s Syndrome (XXY) due to presence of female chromosome (XX)
small firm testicles
gynecomastia (enlarged breast)
azoospermia (presence of semen with no sperm cell)
Condition with ↓ dihydrotestosterone
5-reductase Deficiency
Manifestation of 5-reductase Deficiency
Physical development similar to female phenotype
Cryptorchidism (presence of ambiguous/ undetermined genitalia)
Cryptorchidism is seen in what condition
5-reductase Deficiency
a Hypergonadotropic Hypogonadism (testosterone)
Characterized by muscle dystonia and testicular failure (esp. at 4th decade of life)
Myotonic Dystrophy
involuntary muscle contraction
Muscle dystonia
Testicular failure in myotonic dystrophy usually occurs during this period of life
4th decade of life
aka Sertoli cell-only deficiency
germ cell aplasia
reason of lacking germ cell in Sertoli cell-only deficiency
Aplasia – no cell growth → lack of germ cell
Biopsy of small testis of this condition presents an absence of spermatozoa
Sertoli cell-only deficiency/germ cell aplasia