The impact of repetitive transcranial magnetic stimulation on pituitary hormone levels and cortisol in healthy subjects

Background: Repetitive transcranial magnetic stimulation (rTMS) is a new therapeutic tool in the treatment of affective disorders but only few studies on its safety exist. We aimed to determine the impact of rTMS on (neuro)endocrinological serum levels by a placebo-controlled cross-over study. Methods: 23 healthy subjects were stimulated by rTMS in a typical paradigm used in the treatment of depression (coil placed over left dorsolateral prefrontal cortex, 10 and 20 Hz stimulation). Placebo, infrathreshold, and suprathreshold stimulation were applied in random order. The serum levels of cortisol, prolactin, FSH, and TSH were measured before and after stimulation. Results: After infrathreshold stimulation, cortisol and TSH serum levels decreased mildly but significantly. All other stimulations had no significant impact on hormone levels. In female, but not in male, subjects placebo stimulation yielded a significant increase of prolactin. Conclusions: rTMS as applied for the treatment of depression leads to only very mild and safe changes of hormones. These changes, in particular the decrease of cortisol levels, might explain in part the efficacy of rTMS.