Ovarian Hyperthecosis: FSH and LH Levels
In ovarian hyperthecosis, FSH and LH levels are typically low or normal (not elevated), which distinguishes this condition from polycystic ovary syndrome (PCOS) and is a critical diagnostic feature.
Typical Gonadotropin Pattern
Based on the available research evidence, ovarian hyperthecosis presents with the following gonadotropin characteristics:
- LH levels: Low to normal range 1
- FSH levels: Low to normal range 1, 2
- Key distinction: Absence of the elevated LH or elevated LH/FSH ratio typically seen in PCOS
Clinical Context and Diagnostic Significance
Why This Pattern Matters
The low-normal gonadotropin pattern in ovarian hyperthecosis differs fundamentally from other hyperandrogenic conditions:
- PCOS typically shows: LH <15 IU/L, FSH <10 IU/L, with LH > FSH ratio 3
- Ovarian hyperthecosis shows: Both gonadotropins in low-normal range without the characteristic LH predominance
- This is paradoxical because despite severe hyperandrogenism (testosterone often 2-10 times normal), the hypothalamic-pituitary axis remains suppressed or normal 1
Pathophysiology
The hypothalamic-pituitary physiology in hyperthecosis differs from PCOS 1:
- No tonic LH elevation is present, unlike PCOS
- The luteinized stromal cells in hyperthecotic ovaries produce massive amounts of testosterone and DHT independent of high LH stimulation
- FSH may be the trophic stimulus responsible for the functional activity of luteinized stromal cells, particularly in postmenopausal cases 2
Diagnostic Algorithm
When evaluating suspected ovarian hyperthecosis:
- Measure baseline gonadotropins: Expect low-normal FSH and LH (not elevated)
- Measure testosterone: Typically markedly elevated (often >2-3 times upper limit of normal) 4
- Check DHEAS: Should be normal or only mildly elevated (if >600 µg/dL, consider adrenal tumor) 4
- GnRH stimulation test: Shows normal gonadotropin response (unlike hypogonadotropic hypogonadism) 1
Critical Pitfall
Low LH levels with severe hyperandrogenism should raise suspicion for either ovarian hyperthecosis or androgen-secreting tumor 5. The finding of low serum LH in patients with hirsutism and elevated androgen secretion should alert clinicians to these possibilities rather than PCOS.
Confirmation of Diagnosis
The most definitive confirmation comes from demonstrating ovarian source of androgens 6:
- Ovarian vein sampling shows 10-30 fold gradients in testosterone, androstenedione, and other androgens compared to peripheral blood
- GnRH antagonist test: Rapid (<24 hour) suppression of testosterone with depot GnRH antagonist confirms ovarian source and LH-dependent production 6
Postmenopausal Presentation
In postmenopausal women with hyperthecosis 2:
- FSH and LH may be in the "menopausal range" but are often lower than expected
- Despite menopausal gonadotropins, severe hyperandrogenism persists
- Immunohistochemistry shows luteinized stromal cells are FSH-positive but LH-negative, suggesting FSH (not LH) drives steroidogenesis in this context
Treatment Response Monitoring
Unlike PCOS, ovarian suppression with oral contraceptives often does not improve hirsutism in hyperthecosis, possibly due to the absence of tonic LH elevation 1. This therapeutic failure can be an additional diagnostic clue distinguishing hyperthecosis from PCOS.