Transdermal estrogen replacement therapy in postmenopausal women previously treated for porphyria cutanea tarda

Oral contraceptives and postmenopausal estrogen replacement therapy are rec ognized as risk factors for the development of porphyria cutanea tarda (PCT ) in women. The recommended clinical practice is to withhold estrogen thera py in women who have had phlebotomy therapy for PCT and are clinically and biochemically normal. We tested the safety and efficacy of transdermal estr ogen replacement therapy in 7 women previously treated for PCT and compared them with 19 non-porphyric control subjects treated with transdermal or or al estrogens. Gonadotrophic hormone levels, estrogen levels, liver function studies, body iron stores, urine porphyrin excretion, and cytochrome P4501 A2 (CYP1A2) activity were monitored for 1 year. Four of the women previousl y treated for PCT completed the study. None had evidence of a porphyric rel apse. CYP1A2 activity, measured by three different methods, did not differ between study subjects receiving estrogens, patients with active PCT, and n on-porphyric control subjects, nor did CYP1A2 activity change during the st udy period. Gonadotrophic hormone levels fell and estrogen levels rose in a ll women receiving estrogens. The administration of estrogens by the transd ermal route appeared to be safe in the small number of subjects we studied and should be considered for women previously treated for PCT.