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Summaries for the Public from recent articles in Clinical Thyroidology
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THYROID CANCER
Postmenopausal women whose TSH levels are kept suppressed for treatment of thyroid cancer may have lower bone density.
BACKGROUND
TSH regulates the thyroid and, as thyroid hormone levels increase, TSH levels decrease. After thyroidectomy for thyroid cancer, patients were often placed on levothyroxine doses that were high enough to suppress (turn off) TSH levels to prevent recurrence of the cancer. However, keeping TSH suppressed is no longer recommended for everyone because most patients with thyroid cancer have good prognosis with very low risk of progression or recurrence. Thyroid hormone plays an important role in bone health, and hyperthyroidism, where TSH is low, is known to increase risk of osteoporosis and fractures. Long-term suppression of TSH can result in adverse effects such as irregular heart rhythm or low bone density and osteoporosis. Therefore, the current American Thyroid Association (ATA) guidelines recommend keeping TSH suppressed only in patients with persistent cancer or high risk of recurrence. However, a recent survey showed that many physicians still recommend keeping TSH low in patients with thyroid cancer. Since the majority of patients with thyroid cancer live for many years, these patient may be at a risk of developing adverse effects from long-term TSH suppression.
This study evaluated potential effects of TSH suppression therapy for thyroid cancer on bone density in three different groups of patients.
THE FULL ARTICLE TITLE
Ku EJ et al. 2021 Effect of TSH Suppression Therapy on Bone Mineral Density in Differentiated Thyroid Cancer: A Systematic Review and Meta-analysis. J Clin Endocrinol Metab. Epub 2021 Jul 24. PMID: 34302730
SUMMARY OF THE STUDY
A total of 20 studies were reviewed. Among these, 17 studies with 1824 patients (739 patients with thyroid cancer and suppressed TSH levels and 1085 control patients without thyroid disease) who had bone mineral density (BMD) measurement values were included.
Patients were divided into three groups according to gender and menopausal status since estrogen can affect bone health: 1) postmenopausal women, 2) premenopausal women, and 3) men. The differences in BMD between thyroid cancer patients and controls were compared in each group.
TSH suppression therapy was associated with a lower BMD in lumbar spine in postmenopausal women, although there were no difference in BMD in hip. In contrast, TSH suppression therapy was associated with higher BMD in lumbar spine and hip in premenopausal women. There were no significant difference in BMD in spine or hip in men between TSH suppression therapy group and control group. In the systematic review, two studies showed that postmenopausal women treated with TSH suppression therapy had more decrease in bone density over time compared to control women, with longer duration of TSH suppression therapy associated with more bone loss.
WHAT ARE THE IMPLICATIONS OF THIS STUDY?
Keeping TSH low for treatment of thyroid cancer may be associated with lower bone density in postmenopausal women. However, the adverse effects of TSH suppression therapy on bone density were not seen in premenopausal women or in men. This difference in the effects of TSH suppression therapy for different groups of patients may be related to estrogen or testosterone status, as estrogen and testosterone are known to protect against bone loss. Different groups of patient may have had different dietary habits or physical activity levels, which were not assessed. The overall number of patients included in this study is relatively small. Therefore, larger studies would be helpful in further evaluating the effects of long-term TSH suppression therapy for thyroid cancer on bone health. Overall, the findings of this study are consistent with what we would expect about long-term effects of TSH suppression on bone health in postmenopausal women. It is reassuring that there were no significant adverse effects of TSH suppression therapy on bone health seen in premenopausal women or men. Given the findings, it may be advisable to monitor bone health routinely in postmenopausal women whose TSH is kept suppressed for treatment of thyroid cancer.
— Sun Y. Lee, MD
ATA THYROID BROCHURE LINKS
Thyroid Cancer (Papillary and Follicular): https://www.thyroid.org/thyroid-cancer/
ABBREVIATIONS & DEFINITIONS
Thyroid hormone therapy: patients with hypothyroidism are most often treated with Levothyroxine in order to return their thyroid hormone levels to normal. Replacement therapy means the goal is a TSH in the normal range and is the usual therapy. Suppressive therapy means that the goal is a TSH below the normal range and is used in thyroid cancer patients to prevent growth of any remaining cancer cells.
TSH: thyroid stimulating hormone — produced by the pituitary gland that regulates thyroid function; also the best screening test to determine if the thyroid is functioning normally.
Differentiated thyroid cancer: Types of thyroid cancer that include papillary thyroid cancer and follicular thyroid cancer
Thyroidectomy: surgery to remove the entire thyroid gland. When the entire thyroid is removed it is termed a total thyroidectomy. When less is removed, such as in removal of a lobe, it is termed a partial thyroidectomy.
Cancer recurrence: this occurs when the cancer comes back after an initial treatment that was successful in destroying all detectable cancer at some point.
Bone Mineral Density (BMD): this is usually measured in the lumbar (lower) spine and the hip and the results give information as to the strength of the bone and the risk of fractures. The results are expressed as T scores, which as standard deviations from the average bone density in a person in their 20s, when bone mass is the highest. A T score of -1 to -2.5 is termed Osteopenia and a T score >2.5 is termed Osteoporosis.
Osteoporosis: decrease in bone mineral density in which the individual is at a significantly increased risk for fractures with little or no trauma or force. This occurs with a bone mineral density T score of >-2.5. The areas at highest risk for osteoporotic fractures are the wrist, spine and hip
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