Prolactin in cluster headache: diurnal secretion, response to thyrotropin-releasing hormone, and relation to sex steroids and gonadotropins.

The diurnal rhythmicity of serum prolactin (PRL) and the PRL and thyrotropin (TSH) response to thyrotropin-releasing hormone (TRH) were studied in 31 cluster headache patients (4 chronic cases) and 14 healthy controls. Sixteen of the patients were studied both during clinical remission and headache periods. In males the nocturnal PRL peak was blunted during remissions as compared with that in cluster periods and that in control individuals. The 24-h mean PRL levels were lower during remission and cluster periods than in the controls. There were no significant differences in the PRL levels between female patients and controls. Headache attacks were often associated with increases of serum PRL levels. The PRL response to TRH was lower in the female patients but not in the male patients as compared with controls. The maximum testosterone levels were lower during cluster periods than during clinical remission but not when compared with controls. Serum levels of luteinizing hormone, follicle-stimulating hormone, progesterone, estradiol, T3, T4, and TSH did not differ between patients and controls. The results suggest an altered regulation of PRL secretion not only during active cluster periods but also during symptom-free intervals. The possible influence of sleep, estradiol, testosterone, medication, pain, and serotoninergic and dopaminergic mechanisms are discussed.