If a woman has short cycles and low progesterone as an isolated problem, it is an easy fix. Sometimes there is low estrogen along with low progesterone and this also can be helped, although sometimes with more difficulty as menopause approaches. It is desirable to get three levels (some say five) to assess the luteal phase, the time in the menstrual cycle after ovulation. If ovulation is identified with the last (peak) day of fertile mucus (or with an LH ovulation kit), the hormone levels should be obtained five, seven and nine days thereafter. With at least three levels of progesterone (and estrogen) you get a much better assessment of the luteal phase than just one progesterone level. Luteal phase levels are much more accurate when determined in conjunction with the peak mucus or ovulation day, rather then simply assuming that a certain day (such as day 21 or day 22) is the maximal progesterone day of the cycle.
In your case, it is hard to assess the significance of a single progesterone level on day 23 of a 24 day cycle. This may have been quite a bit later than your highest progesterone level, and could be meaningless. You do not say what units the .80 progesterone value is in. In the USA we use ng/ml and elsewhere nmol/l is used. In the system developed by Dr. Thomas Hilgers the levels 5,7 and 9 days after the peak mucus or ovulation day should ideally be 12, 15 and 12 ng/ml or about 38, 48 and 38 nmol/l respectively. There is some variation among laboratories.
Your 24 day cycle is shorter than the optimal 28-32 day cycle for conception, and almost certainly indicates some type of luteal phase insufficiency. You would be well served by a more thorough workup of the luteal phase. You could learn to detect ovulation with an ovulation NFP method (such as Creighton/Fertilitycare or Billings) or use an LH ovulation detection kit. Then ask your doctor to order three progesterone and estradiol levels on the appropriate days after ovulation. The estradiol levels should be in the range 110-120 pg/ml.
Low progesterone can be treated with luteal progesterone supplements such as progesterone vaginal capsules or progesterone injections. They can be used from the third day through the twelfth day after the peak mucus or ovulation day. Low estrogen can be treated with HCG injections, as well as Clomid or other agents, depending on your situation. For more help with infertility you can find a medical consultant in the FertilityCare (Creighton) method at http://www.fertilitycare.org/ in the U.S. or http://fertilitycare.net/index.html in Europe.
Best wishes,
Mary L. Davenport, M.D