W3006  Physiology      Fall 2002   Problem set #3  -  Female reproduction and sexual differentiation

1.        Indicate whether a>b, a=b, or a<b

A.  a. plasma concentration of progesterone during the follicular phase of the menstrual cycle
      b. plasma concentration of progesterone during the luteal phase of the menstrual cycle

B.  a. length of the luteal phase of the menstrual cycle
     b. length of the secretory phase of the menstrual cycle

C.  a. frequency at which eggs are fertilized in the uterus
     b. frequency at which eggs are fertilized in the oviduct

2.        The hormone that stimulates ovulation also stimulates
a. spermatogenesis       b.testosterone secretion      c. development of the corpus luteum     d. development of uterine glands  

3.  Fill in the blanks

A.  The muscle layer of the uterus is called the _____________________________.

B.    FSH secretion is inhibited by secretion of _______________________ from Sertoli cells. 

C.     ___________________________________ are local hormones, derived from fatty acids, that have a variety of effects, including stimulating smooth muscle contraction and raising the hypothalamic set point for temperature.

4.  The year is 2005.  (I think I wrote this question in 1996!)   You've just opened a medical practice and the federal government and all the insurance companies have just gone bankrupt.  A woman enters your office, wanting to know whether she is ovulating during her menstrual cycles, though she is not concerned about pinpointing the exact time of ovulation.  (In some cycles there is no ovulation, but as estrogen levels gradually fall, menstruation occurs anyway.)  You have enough money to perform just one assay for just one hormone just one time.  Which hormone do you choose (estrogen, progesterone, GnRH, LH, or FSH)?  Why this hormone and not each of the others?  How will you calculate the day to take a blood sample to measure it?

5. The anterior pituitary gland releases gonadotropins, hormones that stimulate the gonads (ovaries) to secrete ovarian hormones (estrogen and progesterone) and to release an egg.  Some women are infertile because they produce insufficient gonadotropins.  They can be treated by injection of a substance isolated from the blood or urine of elderly Italian nuns.  These women are post-menopausal, meaning that their ovaries are no longer producing hormone.
A.        What substance would you expect is in their blood in such high levels? 
B.       Why is it high in these women?

6. . Describe two natural conditions during which a woman might get a false positive response on a home pregnancy test.  (that is, it says she's pregnant but she's really not.)

7.  Italian scientists wondered whether the Pill decreases a woman’s sexual desire by decreasing her ability to detect the enticing smell of a male.  The results are described in the article "Odor and the Pill"  from Eurekalert.org.   Which one hormone would you say is most likely to inhibit ability to smell certain odors?  Explain the information you used to reach this conclusion.

Odor and the Pill

Italian scientists have confirmed that the Pill appears to affect a woman’s sensitivity to smells.

In a study involving 60 non-Pill using women aged 18 to 40 they measured their ability to detect six distinctive substances – anise, musk-ketone, clove, pyridine, citral and ammonia – at three defined times in the menstrual cycle. The testing was done were during the follicular phase (day 5-8), the periovular phase (day 13-16) and the luteal phase (day18-23). The women’s sense of smell was most sensitive at the time around ovulation. The research is published today (Friday 26 October) in Human Reproduction.

The volunteers were then prescribed oral contraceptives ….. After three months’ use the women’s sensitivity to smell was tested again on days 7, 14 and 21 of the 28-day month.

This time there was no difference in the women’s sensitivity to smell between any of the days and the level of sensitivity most nearly matched that of the luteal (pre-menstrual) phase when the women were not taking oral contraceptives.

 

Answers:

1. A.  a<b     B. a=b      C. a<b

2. b. c

3.  A. myometrium   B. inhibin    C.  Prostaglandins

4.   Significant progesterone is secreted only from the corpus luteum, not the follicle, so you'd expect to see progesterone only in the second half of the cycle, and only if ovulation has occurred.  So you'd want to assay in the middle of the luteal phase, but this is hard to pinpoint, since it depends on cycle length.  Best estimate would be to start counting from day 1 of menstruation, and then assay 21-22 days later. If the cycle's exactly 28 days, you'd hit the peak of P secretion.  If the cycle is shorter or longer than 28 days, you'd be at the beginning or end of the luteal phase, so would still be likely to find P.    NOTE: Measuring LH would also indicate the likelihood that ovulation will occur in this cycle, but because the LH peak is very brief (1 day), you're likely to miss this day, considering the lack of equipment available to you.  Same argument holds for FSH and GnRH.  The latter is also not a good choice, because levels in the peripheral blood are so low.  E is high both before AND after ovulation, so if you measure just one point, you won't know which time you're measuring, and whether ovulation occurred.

5.  A. gonadotropins     B.  Since gonadal hormones are lower, there is less negative feedback on the anterior pituitary and/or hypothalamus, and so there will be increased levels of the gonadotropins in the blood.. There will also be increased levels of GnRH in the portal vessel, but this is diluted so much by the time it reaches the general circulation, that it will not be found in significant levels in the urine.

6.  The home preg test measures hCG, which normally has the effect of maintaining the corpus luteum, just like LH does.  In fact, its structure is very similar to that of LH.  High LH can react with the antibodies used in the preg test, so she'll give a positive response if she has high LH.  This can occur naturally just before ovulation, of course.  In addition, it will occur when negative feedback from the ovaries is removed.  This occurs naturally at menopause, when the decreased secretion of ovarian hormones leads to high levels of gonadotropic hormones being measured in the blood.

7.  Progesterone.   Evidence from regular cycle:  Sensitivity to smell was lowest in follicular phase (when E only is present), but it's high just before ovulation (when E is highest), which makes it seem more likely that E increases sensitivity to smell.  Sensitivity is lowest in the luteal phase; the hormone that dominates here is Progesterone, so it's more likely that P  inhibits sensitivity.   OR:  You might say that sense of smell is best just before ovulation when E and LH and FSH reach their peaks, so it's unlikely that any of these are involved, leaving P as the reasonable option.  OR:  You might say that the Pill caused the ability to smell to be "luteal-like", and smell in the luteal phase is lowest, and since P is high in the Pill and in the luteal phase, this is likely to be the hormone that lowers smell ability.  OR: You might say that the Pill today contains both E and P, which is similar to the conditions in the luteal phase;  Smell is lowest whenever P is present (luteal and Pill) and highest when P is absent, so again P is likely.