Are thyroid nodules less likely to be cancerous when I have been taking Synthroid (thyroxine) for 20 years?

Not always. There is a slight increased risk of thyroid cancer in people with hashimoto's thyroiditis, the most common cause of hypothyroidism. If the nodule(s) have been stable for 20 years, they are unlikely to be cancerous. Any new nodules are assumed to be suspicious and should have an ultrasound and possibly a biopsy.
No. Synthroid (thyroxine) treatment for thyroid nodules, regardless of length of treatment, does not affect the risk of thyroid cancer. The decision to biopsy and/or remove the thyroid nodule is made independent of synthroid (thyroxine) use.

Related Questions

Are thyroid nodules more or less likely to be cancerous when one has been taking Synthroid (thyroxine) for 20 years?

Depends. If autoimmune thyroiditis is the reason you are hypothyroid, then there is about a 3 fold increase in risk for developing thyroid cancer over those who don't have anti thyroid antibodies. Having said that, thyroid cancer is still relatively uncommon despite a growing incidence. Read more...
Nodules. No correlation with synthroid (thyroxine) use. Nodule changing to malignancy correlates with age of patient and size of nodule. Older patient more likely to have cancer. Read more...
No effect. The act of taking synthroid (thyroxine) has nothing to do with the potential for thyroid nodules to be cancerous. Radiation exposure, smoking, family history of thyroid cancer elevate the risk for a nodule to be cancerous. The nodules are typically followed by ultrasound over time. If one or more significantly changed in size, biopsy is needed. Read more...

Thyroid nodules on left and right side. Fna showed papillary cancer. Synthroid (thyroxine) 50mcg/day. Nodules dicresed since 4/2012. Okay to wait 6 mo. For surg?

I wouldn't. The longer there is cancer, the longer it can work its way out of the thyroid capsule, grow, and spread via the lymph nodes. As this occurs, the prognostic factors worsen. Read more...
Controversial . Most of the surgeons will advise to under go surgery as soon as possible, as papillary cancer is not as lethal as other malignancies , some of the studies do show with surgery or with out life expectancy is almost same. Ask your doctor and up to you. Read more...

Can 50mcg of Synthroid (thyroxine) make thyroid nodules grow?

NO. Thyroid supplementation occasionally can help to shrink a nodule, and has been used to suppress the growth. Read more...
Thyroid modules. No - generally not. In fact synthroid (thyroxine) is sometimes given in hopes of reducing nodule size. Read more...
No. Synthroid (thyroxine) does not cause thyroid nodules to grow. If you think your nodules/masses are growing, see your doctor for a repeat ultrasound to get the measurements. Often time, people thinks their nodules are growing but they are actually not, thus a repeat ultrasound could be used as a reassurance for you as well. Read more...

I'm confused aftr readng! .Have thyroid nodules. Ws on synthroid (thyroxine).10 yrs later, diff. Dr took off syn. Ok for no treatment w/nodules dr. Rarely ultrasnds?

Evolving knowledge. In the past it is not uncommon for people with thyroid nodules to be started on levothyroxine supplementation. The logic was high dose thyroxine would keep the nodule from growing. Studies have failed to prove this and most endocrinologists gave up the practice of prescribing levothyroxine suppression for thyroid nodules. Most thyroid nodules are benign(>95%) , long history is reassuring in ur cas. Read more...

I'm 20wk preg. Having cold nodules on thyroid gland. Will go for biopsy. On thyroxine tablets. No swelling. Is it cancerous and hope baby is fine.?

Nodule. Baby is fine as long as the thyroid level is normal. Nodules are common and even when it's a "cold" nodule the risk of cancer is still small as well over 80% of them are still benign. I wouldn't worry much about it. I would systematically work it up and see what happens. Good luck. . Read more...
Pregnancy. Thyroid cancer in pregnancy is uncommon. Most thyroid cancers diagnosed during pregnancy can be observed until delivery. If there is a positive biopsy and aggressive clinical behavior (spread to lymph nodes) then surgery during the 2nd trimester might be considered. If this becomes the case, see a surgeon who has experience either this unique situation. Read more...