Should this patient take Synthroid for her subclinical hypothyroidism?

Noriko Noguchi, MD, is an OB/GYN physician in Japan. Her subspeciality is endocrinology.

Simon R. Downes, : A friend of mine has been told by her D.O. that she has subclinical hypothyroidism, and has been recommended to take 50µg of Synthroid. Is it safe, or even indicated in her case?

Can you tell me a little more about your friend?

Well, she has been feeling some brain fog (fatigue, slight confusion) recently, and went to see her D.O. for a basic work-up. Her TSH was slightly elevated at 2.12, with normal T3 & T4 levels. She also has a history of ovarian and breast cysts. For her breast cysts, she had a thermogram to confirm the condition in 2010, and then received 35mg/day of progesterone cream. It was applied in the last 2 weeks of her cycle. This was successful. She has now been using the cream for about 5 years, using about 20mg/day topically. Since July of 2015, she has been using 50mg/day, applying the cream on the inside of her arms. Recently, she has been experiencing early or late menstruation. 

Progesterone cream? Wow! We do not have that in Japan, but we do have estrogen cream. I am wondering if the cream contains some estrogen? As for progesterone, we do have oral progesterone tablets which are used for amenorrhoea or luteal dysfunction.

Firstly, I would like to tell you that in Japan, OB/GYNs do not examine breasts or treat breast concerns. This is for surgeons only. Also, in Japan, we do not treat cysts, although the surgeon may attempt to aspirate the fluid of the cysts.

I think the menstruation problems are due to the progesterone cream. Aslo, I think the brain fog may be related to this too.

So you are saying these are directly related?

Well, it is not my patient, so I can only consider an answer from the information you are providing, but yes, this seems very possible. Let me explain –

As stated above, we give progesterone tablets for ammenorrhea or luteal dysfunction. This can cause brain fog or fatigue (feel sleepy/heavy). After ovulation, progesterone is secreted from the corpus luteum  in the ovaries. You know about PMS – yes? These symptoms are also present with PMS (anxiety, fatigue, sleepy, heavy, irritation, memory lapses).

Regarding the use of estrogen, data shows an increased risk for developing breast cancer with 5+ years of use.

Sometimes post-menopausal women have progesterone + estrogen therapy to prevent cancer of the uterus/endometrial cancer.


Concerning hyperthyroidism, free T3 & T4 would be increased and TSH would be low. For Hypothypoidism, there would be low T3 & T4 and increased TSH.

To really know the condition, I would recommend her to go to an endocrinologist, who would check her levels a number of times over a certain time period. Other antibodies, antigens should be checked too.

Thyroid disease is more common in women than males, and thyroid disease can cause menstrual irregularities and amenorrhoea.

One more thing to consider is Polycystic Ovary Syndrome (PCOS) that can affect a woman’s hormone levels, periods, and ovulation.

Thank you, Dr. Noguchi.