A FSH-secreting pituitary adenoma discovered after ovarian hyperstimulation syndrome: a case report, illustrating pitfalls in the interpretation of serum FSH levels

Normal FSH levels in suspected ovarian hyperstimulation syndrome may indicate an FSH-secreting tumor, highlighting the need for careful hormonal assessment.

Summary and findings

This case report discusses a 29-year-old woman with irregular menstruation who was found to have bilateral ovarian tumors. Hormonal analysis revealed elevated estradiol at 737 pg/ml and low luteinizing hormone, while both follicle-stimulating hormone and human chorionic gonadotropin were within normal ranges. The findings led to the discovery of an FSH-secreting pituitary adenoma, which altered the planned surgical approach.

Abstract

Abstract Background: Most cases of ovarian hyperstimulation syndrome (OHSS) are caused by infertility treatment using human menopausal gonadotropin (HMG) and human chorionic gonadotropin (hCG). OHSS is widely known to have a “spoke-wheel” appearance on imaging, presenting as bilateral symmetric enlargement of ovaries with multiple cysts of varying sizes. When this spoke-wheel appearance is observed in patients not undergoing infertility treatment, tumor-derived hormones such as follicle-stimulating hormone (FSH) and hCG should be measured. However, pitfalls exist in the interpretation of FSH levels. Case presentation: A 29-year-old, gravida 0, para 0 woman visited her local doctor for irregular menstruation and to seek fertility treatment. At the first medical examination, bilateral ovarian tumors were found by ultrasonography, and she was referred to our hospital. Magnetic resonance imaging (MRI) findings of the bilateral ovarian tumors suggested typical OHSS, and thus levels of serum hormones including FSH and hCG were measured to determine whether endogenous follicle-stimulating hormones were the cause. Estradiol was elevated at 737 pg/ml (normal: 28.8-196.8 pg/ml in follicular phase) and luteinizing hormone (LH) was low at < 0.3 mIU/ml (normal: 1.4-15 in follicular phase, 2.1-88 mIU/ml in ovulatory phase). Both FSH and hCG were within normal ranges. Therefore, the ovarian masses seemed to be estrogen-producing neoplasms rather than endogenous OHSS, and surgical resection was scheduled. However, computed tomography of the neck to pelvic region was performed to rule out metastatic ovarian tumors, and indicated a coincidental pituitary lesion, which was pathologically characterized as an FSH-secreting pituitary adenoma. Consequently, the scheduled ovarian surgery was avoided. Conclusions: Awareness of MRI findings of OHSS is important to avoid unnecessary invasive procedures. When treating patients who have suspected OHSS on imaging but whose serum FSH is in the normal range, it is also important to know that an unsuppressed FSH level despite the negative feedback effect of high estrogen can suggest an FSH-producing tumor.

Elsewhere in the HMG (Human Menopausal Gonadotropin) corpus