Long-term phenothiazine treatment does not cause pituitary tumours

In order to explore the possibility that prolactinomas may be caused by prolonged under-inhibition of prolactin-secreting cells we examined the pituitary fossa in 69 patients on long-term phenothiazine treatment. The average duration of treatment was 12.5 years and 55 (80 per cent) of the patients had persistently raised serum prolactin levels. The incidence of radiologically detectable pituitary fossa abnormalities was not significantly different to that in control populations. In 62 per cent of patients the skull x-rays from an earlier admission were available. Comparison of these with earlier films did not show a higher incidence of pituitary fossa abnormalities after prolonged exposure to phenothiazines.