FSH-secreting pituitary adenomas presenting with spontaneous ovarian hyperstimulation syndrome in children and adolescents: two cases, a literature review, and long-term follow-up

OBJECTIVES: Functioning FSH-secreting pituitary adenomas (FSHomas) are exceedingly rare in children; only nine pediatric patients, seven girls and two boys, have been reported previously. In girls, they commonly present with spontaneous ovarian hyperstimulation syndrome (sOHSS). The clinical presentation, management, and long-term outcomes of these tumors remain incompletely characterized. CASE PRESENTATION: We report two girls aged 10.1 and 16 years with prolonged menstrual bleeding and bilateral multicystic ovarian enlargement due to FSHoma-associated sOHSS. Both demonstrated markedly elevated estradiol, suppressed LH, and nonsuppressed (inappropriately normal) FSH, with pituitary adenomas of 14 × 11 × 13 mm and 9 × 9 mm on MRI; immunohistochemistry was FSHβ-positive in both. Case 1 underwent transsphenoidal adenectomy after medical treatment with letrozole and cabergoline; despite residual tumor tissue, she remained stable over 10 years of follow-up. Case 2 underwent transsphenoidal resection but developed recurrent hyperestrogenism and ovarian enlargement 5 years later despite radiological stability of the residual adenoma, and subsequently required emergency surgery for ovarian torsion (excision of the left ovary, right ovarian cystectomy). All 11 pediatric patients, including the present two, were compared for presentation, treatment, and long-term outcome. CONCLUSIONS: These cases provide 10 and 9 years of follow-up after diagnosis. Biochemical recurrence may occur independently of radiological tumor progression, and persistent ovarian stimulation from residual adenoma tissue may cause irreversible complications, including ovarian torsion. Long-term multidisciplinary surveillance with serial hormonal assessment, pelvic imaging, and pituitary MRI is essential, and early pituitary-directed intervention may prevent unnecessary gynecological surgery.