Tiny Thyroid Cancers Grow if TSH is > 2.5mIU/L.

In the past few years we have moved toward the idea that less is more in the management of thyroid cancers.  This is particularly true with small thyroid cancers (microcarcinomas, less than 1.o centimeters) that are common and often incidentally detected. These may never affect the health or mortality of an individual. Only 2% of these tumors grow in patients older than 60, the risk of growth is higher for younger patients.  Regardless, The likelihood of dying specifically as a consequence from these tiny cancers is less than 0.5-0.2%, whereas the potential risk of complications from a surgery can be higher because most thyroid surgeries are being done by low volume, non-endocrine surgeons.  Because of this realization, we now give patients that qualify the option of having their micro-papillary thyroid cancers monitored over time (“active surveillance” at research cancer centers), or they can undergo removal of half of their thyroid or a more extensive thyroidectomy (situation dependent).   To qualify for active surveillance  there must not be worrisome lymph nodes in the neck, the tumor needs to centrally located in the gland or lobe away from vital structures, and  have nice edges than allow for accurate sequential measures every 6-12 months. Further, the patient must be an active participant who is  comfortable living with thyroid cancer of unclear indolence. If there is progression they can go to proceed to surgery.

This month, a publication by Hye In Kim etal. in the Journal of Clinical Endocrinology and Metabolism sheds more light on how to manage better patients under active surveillance.

Methods: The investigators monitored the growth of these little thyroid cancers by ultrasound measurements for about 2 years in 126 patients.  They also monitored  thyroid function of the patients, in order to see if there was a relation between thyroid status and cancer growth.

Results: Over this surveillance-time 26 patients or 19.8 percent of patients had growth progression in their tumors.  Interestingly, patients that had  higher TSH (thyroid stimulating hormone) levels (greater than 2.5 mIU/L) had a 3.5 fold higher risk of having their papillary thyroid cancers progress in growth.

Educational sidebar: TSH, secreted by the pituitary, is a normal stimulator of thyroid hormone production by thyroid gland.  The higher TSH secretion and blood levels tell  the thyroid gland to make more thyroid hormone to achieve balance. This occurs because the pituitary is sensing that thyroid hormone levels are lower than they should be for that unique person’s metabolic balance.  If the thyroid gland is sick as in Hashimotos or has been removed, one must replace thyroid hormone to restore the TSH to lower normal levels.  What most people do not know is that TSH is also a growth factor for thyroid cancer initiation and progression.  This is why we give higher doses of thyroid hormone to higher risk patients with advanced and/or aggressive variants of thyroid cancer .  We are trying to suppress TSH secretion and its potential to stimulate thyroid-tumor growth or recurrence. Further this why we keep TSH in the lower aspect of the normal range (0.4-2.5 mIU/L) in low risk thyroid cancer survivors.

My take and conclusions: The findings in the study are important because tiny thyroid cancers are considered a common and relatively benign condition by most of us endocrinologists. To date TSH range has not been considered of relevance for monitoring this condition, and most patient’s thyroid levels are considered “normal” if they fall within the 0.4-4.5 mIU/L  A range of TSH held by most labs and adhered to by the average doctor or endocrinologist. These normal levels are seemingly too high for patients with papillary thyroid microcarcinomas. The investigators recommend keeping TSH in the low normal range 0.4-2.5 mIU/L based on their data. this is as discussed the range we want for our low risk thyroid cancer patients who have undergone thyroidectomy.

Reference: Hye In Kim etal. High serum TSH levels Associated with Progression of Papillary thyroid micro carcinomas during active surveillance. JCEM, Volume 103, Issue 2, 1 February 2018, pages 446-451.

Posted in Cancer, prevention of endocrine disease, Thyroid, thyroid cancer