When FSH Misleads: A rare case of isolated FSH elevation — ASN Events
  1. Schedule
  2. Joint Poster Session
  3. When FSH Misleads: A rare case of isolated FSH elevation

When FSH Misleads: A rare case of isolated FSH elevation (#461)

Richard Yang 1 , Daniel Wei 2 , Joyce Wu 2 , Rohit Rajagopal 1
  1. Endocrinology, Campbelltown and Camden Hospitals, Sydney, NSW, Australia
  2. Douglass Hanly Moir Pathology, Macquarie Park, NSW, Australia

Background:

Elevated follicle-stimulating hormone (FSH) in females often suggest diminished ovarian reserve. These cases are usually accompanied by elevated luteinizing hormone (LH), low oestradiol, and menstrual irregularities. In contrast, isolated FSH elevation with normal LH and normal to high oestradiol is unusual.

Case:

We present a case of isolated FSH elevation in a 30-year-old woman referred by gynaecology, being investigated for subfertility. Her history included endometriosis and asthma; not on regular medications. She had menarche at age 12 and maintained regular menstrual cycles. Obstetric history was notable for a miscarriage at 9 weeks, two years prior. FSH had been elevated for at least three years, reaching peak 70.8 IU/L, with consistently normal LH (3.6–5.8 IU/L), and oestradiol (99–500 pmol/L). Ovulation was biochemically confirmed while not pregnant (progesterone 43.9 nmol/L). Testosterone (1.0 nmol/L), anti-Müllerian hormone (18 pmol/L), and inhibin (116 ng/L) were within normal ranges. The remainder of the pituitary profile was unremarkable. MRI head showed no gross pituitary abnormalities. Genetic testing confirmed normal 46XX karyotype without Fragile X. Repeat testing confirmed isolated FSH elevation (36.4 IU/L). Following polyethylene glycol (PEG) precipitation, FSH decreased to 13 IU/L, consistent with FSH bound to high-molecular weight complex (macro-FSH). Heterophilic antibody interference was excluded through additional testing. 5 years post review, FSH remained elevated with low recovery following PEG precipitation across four different assays. In between, the patient conceived naturally with an uneventful pregnancy and maintained regular menstrual cycles.

Discussion:

There is limited data on macro-FSH, but macro-hormones are generally considered biologically inactive. Currently, only 6 cases of macro-FSH (all females) have been reported in literature. We are the first to describe long-term clinical follow-up outcome for a patient with macro-FSH. The preservation of ovarian function and absence of clinical sequelae over time support the hypothesis that macro-FSH is biologically inactive.