Background: Although tamoxifen has been shown to be fairly safe and effective for idiopathic pubertal gynecomastia, it remains unknown whether it is also beneficial for gynecomastia associated with endocrine disorders. Here, we report the effect of tamoxifen on pubertal gynecomastia in 2 siblings with partial androgen insensitivity syndrome (PAIS). Case Reports: Cases 1 and 2 presented with persistent pubertal gynecomastia at 13 and 16 years of age, respectively. Physical examinations revealed breast of Tanner stage 3 and normal male-type external genitalia in both cases. Clinical features such as female-type pubic hair and borderline small testis indicated mildly impaired masculinization. Results: Molecular analysis identified a previously reported p.Arg789Ser mutation in the androgen receptor gene (AR) in the 2 cases. Two months of oral administration of tamoxifen ameliorated gynecomastia to Tanner stage 2 with no adverse events. Additional treatment with testosterone enanthate showed negligible effects on body hair and penile length. Hormone values of the 2 cases during tamoxifen treatment remained similar to those in previously reported untreated patients with PAIS. Conclusion: The results indicate that tamoxifen was effective in treating pubertal gynecomastia in these 2 patients with PAIS and may be considered as a therapeutic option in this situation pending further studies.

Keywords:
Androgen, Gynecomastia, Partial androgen insensitivity syndrome, Tamoxifen, Selective estrogen receptor modulator
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2014
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