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Subclinical Hyperthyroidism and Conception

Last Updated: · Doctors


I am following a 39 y/o woman with 1ry infertility found by her fertility GYN to have a low tsh and diagnosed by myself as having a subclinically hyperthyroid multinodular goiter[-ve fna]. Her TSH has fluctuated between .04 and .15 or so with normal free T4 and T3total. She has no overt hyperthyroid symptoms. She is anxious to try fertility treatments asap due to her age. She has had a fluctuating asymptomatic low WBC count for years[2000s-5000s]. Can you help us quantify the risks of:

1.Proceding with fertility drugs and going through the pregnancy without treatment.[?risk of congenital anomalies, etc.] 2.Versus using low dose ptu[with care re: her wbc's] 3.Versus surgery 4.Versus RAI[and the possiblity it may shorten her remaining reproductive years] She is favoring option number one.

Thank you.

Dr. H B, Indiana


In patients with subclinical hyper- an increased risk for development of atrial fibrillation and decrease in bone mass in postmenopausal women have been described and in such cases treatment must be considered. We don't have data, as far as I know, regarding subclinical hyperthyroidism and subfertility in females. Also, we don't have data regarding subclinical hyper- and congenital anomalies. On the contrary, we have some good papers regarding sublinical hypothyroidism and subfertility. With that in mind, one could proceed with fertility drugs and ignore the suppressed TSH. There is of course a need for close follow-up throughout the pregnancy. Alternatively, small doses of PTU or CMZ (25-50 mg PTU or 2,5-5 mg CMZ) can be used in order TSH levels to become normal. Such doses of antithyroid drugs do not affect wbc. RAI may indeed shorten her remaining reproductive years as usually we have to wait for at least 6 months after treatment efore we suggest the patient to try conception. If I were at her physician's place, I would try first with fertility drugs for 3 months and no treatment for her thyroid. In case of no conception, then I would reconsider my decision.


Gerry Krassas, MD