[A new cause of prolonged fever of unknown origin: progesterone substitution therapy]

Over the last 3 years, we examined 15 patients on progesterone substitution therapy who presented prolonged fever. Many explanations had been put forward before the diagnosis was suggested. We recall the thermogenic effect of progesterone.

Based on a retrospective analysis, we reported the clinical and biological features of 15 patients with prolonged fever due to progesterone substitution therapy and prospectively followed the temperature curves of 9 menopaused women who received substitution therapy for the first time.

The 15 case reports were quite typical. Often onset occurred with an acute infectious episode. Following this episode, the patients continued to take their temperature and discovered persistent fever. The context was often one of anxiety-depression rich in functional symptomatology. Laboratory findings included a normal sedimentation rate in all patients. Several days after treatment withdrawal temperature returned to normal. The prospective study confirmed the thermogenetic effect of almost all progesterone substitution drugs.

The thermogenic effect of natural progesterone is well known but it must be recalled that all progesterone agents with 5-beta metabolites have the same effect. Since metabolic clearance is long, the thermogenic effect may persist for several days after withdrawal.