Unit 8 - Screencasts Flashcards
What type of feedback is exerted by gonadal steroids under typical conditions?
a) Positive feedback on GnRH and LH/FSH
b) No feedback
c) Negative feedback on both GnRH and LH/FSH
d) Short-loop feedback from LH/FSH to GnRH
c) Negative feedback on both GnRH and LH/FSH
Explanation: Under normal physiological conditions, testosterone, estradiol, and progesterone exert negative feedback on both the hypothalamus (GnRH) and anterior pituitary (LH/FSH) to regulate their own production.
What would happen to LH and FSH levels in a male who takes anabolic steroids?
a) They would increase
b) They would decrease
c) They would stay the same
d) FSH would increase, LH would decrease
b) They would decrease
Explanation: Exogenous testosterone (anabolic steroids) mimics high gonadal steroid levels, triggering negative feedback on GnRH and pituitary LH/FSH, reducing their levels and impairing natural testosterone production.
What is the one exception to negative feedback by estradiol?
a) During ovulation, estradiol causes LH/FSH suppression
b) During sustained high estradiol, it triggers positive feedback and the LH surge
c) Estradiol always suppresses GnRH
d) Estradiol suppresses testosterone production
b) During sustained high estradiol, it triggers positive feedback and the LH surge
Explanation: Sustained high levels of estradiol for several days cause a positive feedback loop that leads to a surge in LH (and FSH), triggering ovulation—an unusual example of positive feedback in endocrinology.
Which hormone is produced first in the steroidogenic pathway of both males and females?
a) Progesterone
b) Testosterone
c) Estradiol
d) DHT
a) Progesterone
Explanation: Progesterone is an early product in the steroidogenic pathway. Testosterone and estradiol are derived downstream, with estradiol being synthesized from androgens like testosterone.
Which hormone must be produced as an intermediate before estradiol can be synthesized?
a) Progesterone
b) Estrone
c) Cortisol
d) Testosterone
d) Testosterone
Explanation: Estradiol, the primary estrogen, is synthesized from testosterone via the aromatase enzyme in ovarian cells. Thus, all estrogens are derived from androgens.
What is the releasing hormone for the gonadal axis and what hormones does it stimulate?
a) CRH → ACTH and GH
b) TRH → TSH and prolactin
c) GHRH → GH and IGF-1
d) GnRH → LH and FSH
d) GnRH → LH and FSH
Explanation: GnRH (gonadotropin-releasing hormone) is secreted by the hypothalamus and stimulates the anterior pituitary to release LH and FSH, which act on the gonads.
Which condition in females causes high LH and FSH due to low gonadal steroid production?
a) Pregnancy
b) Ovulation
c) Menopause
d) Oral contraceptive use
c) Menopause
Explanation: In menopause, ovarian function declines and steroid production falls. This removes negative feedback, resulting in increased GnRH, LH, and FSH levels.
Why is the term ‘short-loop feedback’ crossed out in the reproductive axis diagram?
a) There is no evidence that LH/FSH inhibit GnRH
b) LH and FSH suppress GnRH
c) Steroids do not inhibit GnRH
d) It only applies to the thyroid axis
a) There is no evidence that LH/FSH inhibit GnRH
Explanation: Unlike some other endocrine axes, there is little to no evidence for short-loop feedback in the reproductive axis, so this term is excluded.
