Q. Your discussion of Autoimmune Oophoritis (in Overcoming Infertility) piqued my interest because I was just diagnosed with slight hypothyroidism for which I am taking Synthroid. I will be undergoing new day 3 FSH levels in a couple of weeks after having been on the medication for the last month, in the hope that my FSH levels are back to normal or at least below 10.

I do not have painful enlargement of the ovaries, but I gather that autoimmune oophoritis might not show up as the painful enlargement of the ovaries until all the follicles have been burned out. You say that tissue antibodies such as thyroid antibodies are looked for, however they are rarely present. What I can't figure out is, if thyroid antibodies are present (like with me) and the ovaries aren't enlarged, and the thyroid problem is corrected, what happens? Can some good follicles be left? If so, if FSH levels start looking good again is there some hope?

There are real connections between an underactive thyroid and problems with ovulation. But neither thyroid disease nor primary ovarian failure is rare. In practice, the association is often a coincidence.

These are the relevant facts.

• underactivity of the thyroid gland (hypothyroidism) is often caused by an immune reaction against the thyroid gland
• when this happens, your blood levels of thyroid stimulating hormone (TSH) go up and there are thyroid antibodies in the blood
• if you have a reason to look for them, thyroid antibodies are detectable before the thyroid's function is significantly disturbed
• when high TSH levels cannot compensate, a very underactive thyroid gland causes your metabolism to slow
• if the metabolism of FSH is slowed, serum FSH levels will rise, while the menstrual cycle lengthens and bleeding gets heavier (for a whole bunch of reasons associated with generally slowed metabolism)
• treatment with thyroxin (Synthroid) will reverse a rise in serum FSH
• in this circumstance primary ovarian failure is rarely caused by an immune reaction against the ovaries (autoimmune oophoritis)
• when this happens the ovaries usually enlarge and get painful
• in autoimmune oophoritis, whether painful or not, there's a high chance that antibodies will also form to other glands (like the thyroid) because this stage of autoimmune oophoritis might have been missed (and because measuring ovarian antibodies is not always reliable)
• some doctors screen everyone with premature ovarian failure for all sorts of potentially important autoimmune diseases (including thyroid antibodies - which are reliably detectable)
• whatever the cause of primary ovarian failure, serum FSH levels rise
• this rise in serum FSH precedes the periods stopping, occurring as the follicular phase gets shorter; but it's only detectable at the start of the cycle (e.g. on day 3)

Another way of assessing whether a rise in day 3 FSH levels indicates low numbers of follicles is to use transvaginal ultrasound to look at the number of small developing follicles on about day 6 of the cycle, before the dominant follicle is selected by the ovary.

Incidentally, an overactive thyroid gland (hyperthyroidism, or thyrotoxicosis) is more likely to cause infertility or rmiscarriages than an underactive gland.

There's more on infertility and miscarriages in Overcoming Infertility.