Male Gonadal Disorders - Exam 4 Flashcards
Hypothalamic-Pituitary-Gonadal (HPG) first becomes active at ______. What hormones are made where? How often is it released?
puberty
Hypothalamus secretes GnRH, stimulating the anterior pituitary to release FSH and LH
pulsatile release every 2 hours
____ stimulates the _____cells of the testes to regulate ______ and produce ____. ______ provides a _____ feeback
FSH
Sertoli cells
spermatogenesis
inhibin B
inhibin B
negative feedback
____ stimulates ______ synthesis in the _____ cells of the testes. _____ provides a negative feedback and assists ____ in spermatogenesis
LH
testosterone
Leydig
testosterone
FSH
____ attaches to the ____ cells via LH receptor which stimulates ?????
LH
Leydig
the uptake of cholesterol by the cellular mitochondria and initiates steroidogenesis
What 2 things can testosterone be converted to? Where does the conversion take place?
Dihydrotestosterone¹ (DHT) or Estradiol
takes place in the peripheral tissues
testosterone plus _____ (enzyme) = Dihydrotestosterone
testosterone plus _____ (enzyme) = estradiol
5alpha- reductase
CYP12 (also called aromatase)
**90% of testosterone is ______. What are some functions of testosterone?
excreted
Wolffian duct
bone formation
muscle mass
spermatogenesis
sexual health (libido, erection, orgasm)
mood/behavior (increases aggression, decreases anxiety/depression, provides sense of mental well-being)
improves congnition/memory
**What are some functions of DHT?
external genitalia
prostate growth
acne
facial/body hair
scalp hair loss
**What are some functions of estradiol?
hypothalamic/pit feedback
bone reabsorption
growth plate closure
gynecomastia
vascular and behavioral effects
95% of circulating testosterone is synthesized in the _____, the remainder is produced by the _____. How much is active?
testicles
adrenal gland
only the remaining 2% is in active form
Name the 2 plasma proteins that testosterone is bound to. Which one has a greater affinity?
**sex hormone–binding globulin¹ (SHBG) (60%) - has greater affinity
albumin (38%)
____ of testosterone is unbound (physiologically active). Can testosterone unbind easily?
2%
albumin bound testosterone can dissociate readily in the capillaries becoming an active hormone
Testosterone is metabolized in the ___and excreted in the ___
liver
kidneys
What layer of the adrenal gland makes greater amounts of androgens? What age does it start?
zona reticularis
between 6-8 years old
What is sex maturation accelerated by? What is produced? How old?
sex maturation is accelerated by the activation of the HPG axis and the production of GnRH, LH, FSH and testosterone
begins around 9
What are the stages of male development called?
Tanner Stages 1-5
Prepubertal, no pubic hair. What tanner stage?
stage 1
sparse, straight pubic hair along the base of the penis, enlargement of testes and scrotum, scrotal skin reddens and changes in texture. What Tanner stage?
stage 2
Hair is darker, coarser and curlier and extends over the mid-pubis. enlargement of the penis and further growth of the testes. What tanner stage?
stage 3
Hair is adult-like in appearance but does not extend to thighs. increased size of penis with growth in breadth and development of glans, testes and scrotum larger, scrotal skin darker. What tanner stage?
stage 4
hair is adult like in appearance and extends from thigh to thigh, full adult genitalia. What tanner stage?
stage 5
How do you measure testicle size? Prepubertal size is ____. Pubertal is ____/ Adult are _____
Prader orchidometer - beads labeled by volume
Prepubertal sizes are 1 to 3 mL
Pubertal sizes are 4 to 12 mL
Adult sizes are 12 to 25 mL
If you do NOT have orchidometer, what size do the testicles have to be in order to be considered “entered puberty’?
Testicular size >2.5 cm longitudinally generally indicates that the child has entered puberty
What is precocious male puberty defined as? What do you need to document?
evidence of puberty in boys before age 9
the patients Tanner stage
What are the 2 types of precocious puberty. Define them
Isosexual - premature development of phenotypically appropriate secondary sexual characteristics
Heterosexual - development of secondary sexual characteristics of the opposite sex
What are the 2 subtypes for isosexual precocious puberty
gonadotropin-dependent (central precocious puberty [CPP])
gonadotropin-independent - (peripheral precocious puberty)
What is central precocious puberty? Is it gondadotropin independent or dependent?
premature activation of the GnRH pulse generator leading to inappropriately elevated gonadotropin (LH/FSH) levels for age
gonadotropin-dependent
What is peripheral precocious puberty? Is it gondadotropin independent or dependent?
androgens from the testis or the adrenal glands are increased, with low levels of gonadotropins
gonadotropin-independent
What are the 3 causes of central Isosexual Precocious Male Puberty? Which one is MC?
- Idiopathic** MC
- Hypothalamic hamartoma or other lesions
- CNS tumor or inflammatory state
What are 5 causes of peripheral Isosexual Precocious Male Puberty
- Congenital adrenal hyperplasia
- hCG/androgen-secreting tumor
- McCune-Albright syndrome
- Familial male-limited precocious puberty
- Exogenous androgens
If you are concerned about central precocious puberty, what is the first thing you need to exclude? How? What are some historic red flags? PE red flags?
CNS lesions
brain MRI with contrast
historical red flags: headaches, new onset seizures, memory or personality changes, loss of balance, visual changes, N/V,
PE red flags: abnormal neurologic exam (weakness, numbness, tingling)
Peripheral precocious puberty is caused by ??? Where are some common locations?
hCG activates the LH receptors on the Leydig cells stimulating testosterone production
tumor locations
gonads, brain, liver, retroperitoneum, and anterior mediastinum
What is virilization?
the development of male physical characteristics in a female or precociously in a male
What is McCune -Albright syndrome? Is it more common in females or males?
Acquired mutation in the Gsα subunit activating adenylyl cyclase resulting in steroidogenesis stimulating testosterone production
MC- females
McCune- Albright syndrome is an acquired mutation in the _____ activating ______ resulting in ????
Gsα subunit
adenylyl cyclase
steroidogenesis stimulating testosterone production
What is the triad for McCune-Albright syndrome?
bone dysplasia: limping, pain or fracture cafe-au-lait skin pigmentation precocious puberty
McCune Albright Syndrome can also stimulate other endocrine systems, give 3 examples
thyrotoxicosis
growth hormone excess (gigantism or acromegaly)
Cushing Disease
Familial male-limited precocious puberty is peripheral or central? What is it caused by?
An autosomal dominant disorder caused by activating mutations in the LH receptor, leading to testosterone synthesis
Familial male-limited precocious puberty is an ______ disorder caused by _______. What does it lead to?
autosomal dominant disorder
activating mutations in the LH receptor
leading to testosterone synthesis
What is an important hx question to ask a pt for precocious male puberty?
When did dad/brothers do through puberty? What age?
Any hx of exogenous sex steroid exposure?
The size of ____ can help differentiate between central and peripheral causes. Why?
testicles
if HPG axis has activated (central) the sertoli cells will increase in number leading to a larger testicle
peripheral causes the HPG is not activated and there is excessive testosterone but no FSH, so the Sertoli cells will not be larger and the testicle will remain small
If one testicle is larger than the other, what are you thinking?
testicular tumor secreting hCG- peripheral precocious puberty
What is an imaging tool that is used to assess precocious puberty? How do you interpret it?
assesses bone age of the LEFT wrist and hand
rapid growth/change indicative of high concentrations of sex steroids due to CPP or peripheral precocity
slow change: benign pubertal variant with low sex steroid concentration
What is step 1 in dx precocious male puberty?
serum testosterone will be high (high in both central and peripheral causes)
serum LH and FSH
high in central
low/normal in peripheral
What is step 2 in dx precocious male puberty?
figure out if it is central or peripheral
**What do you do if the LH/FSH test are borderline high or on the upper limit of normal?
GnRH-analogue stimulation test
give leuprolide which stimulates the anterior pituitary to release LH/FSH
central: LH will rise because the HPG axis is active
peripheral: no rise in LH because the HPG axis is still inactive
**When is leuprolide used?
as part of the GnRH-analogue stimulation test to figure out if the cause is central or peripheral.
central: LH will rise
peripheral: no change in LH