Serum thyroid-stimulating hormone is elevated in men with Gleason 8 prostate cancer

To measure the levels of serum thyroid- stimulating hormone (TSH) in men with prostate cancer, as those with a Gleason score of > or = 8 are at high risk of skeletal metastases (and should be considered for bone scintigraphy at diagnosis), and because the structural integrity of the skeleton depends on constant remodelling controlled by many local and systemic factors, including TSH, an important regulator of this process.

We evaluated 51 men referred for treatment of localized prostate cancer and 10 with biopsy-confirmed benign prostatic hypertrophy. Serum TSH was determined with a chemoluminescent immunoassay and a commercially available instrument (Immulite, Diagnostic Products Corporation, Los Angeles).

There was significant variation in TSH levels with Gleason score (P = 0.004); men with Gleason 8 tumours had the highest serum TSH levels. Because serum TSH levels increase with age, we used a multivariate analysis of variance with both age and Gleason score as covariates. The effect of Gleason score on TSH level was significant (P = 0.036) and independent of the effect of age (P = 0.392).

We propose that the high serum TSH levels in men with Gleason 8 prostate cancer is a result of the elaboration of TSH by cancer cells. Bone mineral density in the face of normal levels of thyroid hormone depends on an intact response to TSH, which ordinarily suppresses both osteoblast and osteoclast differentiation, thereby exerting control over bone remodelling. However, with abnormally high TSH levels this process may become deranged, promoting the development of bone metastases. If TSH production by prostate cancer cells could be suppressed, the incidence of bone metastases might be reduced.