I am 29, and my husband and I have been trying to conceive for over a year. Recently, my mother mentioned her longstanding thyroid problem. I brought this up to my primary care physician, and sure enough, I have hypothyroidism. I now am taking .05mg of Synthroid. My cycle has always been long. Typically, it is about 32 days. However, every three or four months, I'll have a longer one, about 36-42 days. Is a long cycle a symptom of hypothyroidism? Should I expect to see my cycle length shorten with the Synthroid? Given that my doctor didn't give me a full thyroid profile until I asked for it, are there any other tests I should ask for?

Adrienne

Thyroid disorders can cause many problems with your periods. They may become irregular, come further apart, be heavier than normal or cease altogether. It is impossible to predict how each individual will respond to an abnormality in thyroid gland function.

You mentioned that your physician did not do a complete thyroid profile. In fact, the full panel is rarely helpful. The most pertinent test is the one that checks for thyroid-stimulating hormone (TSH). This hormone is produced by the pituitary gland and stimulates the thyroid to get busy and release its hormones into the bloodstream.

The thyroid gland produces hormones called T3 and T4. The thyroid panel measures only the T4 level. The effect of thyroid hormone on the body's functions depends on the balance between both T3 and T4. The hypothalamus gland measures this balance and signals the pituitary to secrete the amount of TSH necessary to keep thyroid function normal. So, measuring TSH is the best approach to detecting thyroid problems.

Once thyroid hormone replacement begins, it takes about three or four weeks for the body to adjust to the dose. At that point the TSH should be measured to determine if the correct response has been achieved. Within two or three months after you reach a normal TSH level, charting your periods and taking basal body temperatures should demonstrate a return to normal ovulation. If not, it is likely that your menstrual disorder is not related to thyroid function.