APMLE Part 1 Endocrine Physiology Questions With
Complete Solutions
What is familial hypocalciuric hypercalcemia FHH?
autosomal dominant disorder with decreased urinary Ca+2
excretion and increased serum Ca+2
Caused by inactivating mutations of Ca+2 sensing receptor that
regulate PTH secretion
What does vitamin D cause in adults vs. children?
children - rickets
adults - osteomalacia
What enzyme catalyzes the active form of vitamin D?
1α-hydroxylase.
What increases 1 alpha hydroxylase activity?
1) Decreased serum calcium
2) Increased PTH
3) Decreased serum phosphate
What are the actions of 1,25 dihydroxycholecalciferol?
Coordinated basically to increased BOTH CA+2 and
PHOSPHATE in ECF to mineralize bone
,1) Increased intestinal Ca+2 absorption via vit. D dependent
Calbindin D-28K is induced by 1,25 dihydroxycholecalciferol
PTH increased intestinal Ca+2 absorption indirectly by
stimulation 1alpha hydroxylase and increasing production of
vitamin D
2) Increased intenstinal PHOSPHATE absorption
3) Increased renal reabsorption of Ca+2 and phosphate,
analogous to its action in the intestine
4) Increases bone resorption which provides Ca+2 and
phosphate absorption
5) Increases bone resorption which provides Ca+2 and
phosphate from old bone to mineralized new BONE
What secretes calcitonin?
Parafollicular cells of the thyroid
What are the actions of calcitonin?
Secretion is stimulated by Ca+2 and it acts to INHIBIT BONE
RESORPTION and can be used to treat hypercalcemia
What two hormones do the testis secrete?
Antimullerian hormone and testosterone
During development what do testerone and antimullerian
hormone do?
,Testosterone stimulates the growth and differentiation of the
wolffian ducts which develop into the male internal genital tract
Antimullerian hormone causes the atrophy of the mullein ducts
What hormone does the ovaries secrete in development?
Secrete estrogen
During development why do the antimullerian ducts develop?
Without testosterone, the wolffian ducts do not differentiate.
Without antimüllerian hormone, the müllerian ducts are not
suppressed and therefore
develop into the female internal genital tract
What cells secrete and synthesize testosterone?
Leydig Cells
Why do leydig cells not also produce glucocorticoids or
mineralocorticoids?
DO NOT CONTAIN 21β-hydroxylase or 11β-hydroxylase (in
contrast to the adrenal cortex) and, therefore, do not synthesize
glucocorticoids or mineralocorti-
coids.
What converts testosterone into its active form?
Accessory sex organs (e.g., prostate) contain 5`-reductase,
which converts testosterone to
its active form, dihydrotestosterone
What secretes GnRH?
, arcuate nuclei of the hypothalamus secretes GnrH which causes
LH and FSH secretion
What cells does FSH act on?
the sertoli cells to maintain spermatogenesis
What cells secrete inhibin?
sertoli cells, inhibit FSH secretion
How does testosterone act in the testis?
Testosterone acts via an intratesticular paracrine mechanism to
reinforce the spermatogenic effects of FSH in the Sertoli cells.
What provides negative feedback for LH?
Testosterone inhibits the secretion of LH by inhibiting the
release of GnRH from the hypo- thalamus and by directly
inhibiting the release of LH from the anterior pituitary.
What are the main actions of tester one?
■ Differentiation of epididymis, vas deferens, and seminal
vesicles
■ Pubertal growth spurt
■ Cessation of pubertal growth spurt (epiphyseal closure)
■ Libido
■ Spermatogenesis in Sertoli cells (paracrine effect)
■ Deepening of voice
■ Increased muscle mass
Growth of penis and seminal vesicles
■ Negative feedback on anterior pituitary
What occurs hormonely durign puberty?
Complete Solutions
What is familial hypocalciuric hypercalcemia FHH?
autosomal dominant disorder with decreased urinary Ca+2
excretion and increased serum Ca+2
Caused by inactivating mutations of Ca+2 sensing receptor that
regulate PTH secretion
What does vitamin D cause in adults vs. children?
children - rickets
adults - osteomalacia
What enzyme catalyzes the active form of vitamin D?
1α-hydroxylase.
What increases 1 alpha hydroxylase activity?
1) Decreased serum calcium
2) Increased PTH
3) Decreased serum phosphate
What are the actions of 1,25 dihydroxycholecalciferol?
Coordinated basically to increased BOTH CA+2 and
PHOSPHATE in ECF to mineralize bone
,1) Increased intestinal Ca+2 absorption via vit. D dependent
Calbindin D-28K is induced by 1,25 dihydroxycholecalciferol
PTH increased intestinal Ca+2 absorption indirectly by
stimulation 1alpha hydroxylase and increasing production of
vitamin D
2) Increased intenstinal PHOSPHATE absorption
3) Increased renal reabsorption of Ca+2 and phosphate,
analogous to its action in the intestine
4) Increases bone resorption which provides Ca+2 and
phosphate absorption
5) Increases bone resorption which provides Ca+2 and
phosphate from old bone to mineralized new BONE
What secretes calcitonin?
Parafollicular cells of the thyroid
What are the actions of calcitonin?
Secretion is stimulated by Ca+2 and it acts to INHIBIT BONE
RESORPTION and can be used to treat hypercalcemia
What two hormones do the testis secrete?
Antimullerian hormone and testosterone
During development what do testerone and antimullerian
hormone do?
,Testosterone stimulates the growth and differentiation of the
wolffian ducts which develop into the male internal genital tract
Antimullerian hormone causes the atrophy of the mullein ducts
What hormone does the ovaries secrete in development?
Secrete estrogen
During development why do the antimullerian ducts develop?
Without testosterone, the wolffian ducts do not differentiate.
Without antimüllerian hormone, the müllerian ducts are not
suppressed and therefore
develop into the female internal genital tract
What cells secrete and synthesize testosterone?
Leydig Cells
Why do leydig cells not also produce glucocorticoids or
mineralocorticoids?
DO NOT CONTAIN 21β-hydroxylase or 11β-hydroxylase (in
contrast to the adrenal cortex) and, therefore, do not synthesize
glucocorticoids or mineralocorti-
coids.
What converts testosterone into its active form?
Accessory sex organs (e.g., prostate) contain 5`-reductase,
which converts testosterone to
its active form, dihydrotestosterone
What secretes GnRH?
, arcuate nuclei of the hypothalamus secretes GnrH which causes
LH and FSH secretion
What cells does FSH act on?
the sertoli cells to maintain spermatogenesis
What cells secrete inhibin?
sertoli cells, inhibit FSH secretion
How does testosterone act in the testis?
Testosterone acts via an intratesticular paracrine mechanism to
reinforce the spermatogenic effects of FSH in the Sertoli cells.
What provides negative feedback for LH?
Testosterone inhibits the secretion of LH by inhibiting the
release of GnRH from the hypo- thalamus and by directly
inhibiting the release of LH from the anterior pituitary.
What are the main actions of tester one?
■ Differentiation of epididymis, vas deferens, and seminal
vesicles
■ Pubertal growth spurt
■ Cessation of pubertal growth spurt (epiphyseal closure)
■ Libido
■ Spermatogenesis in Sertoli cells (paracrine effect)
■ Deepening of voice
■ Increased muscle mass
Growth of penis and seminal vesicles
■ Negative feedback on anterior pituitary
What occurs hormonely durign puberty?
