From the Guidelines
In PCOS, LH levels are elevated while FSH levels remain normal or low due to disruptions in the hypothalamic-pituitary-ovarian axis, as evidenced by the most recent study 1. This hormonal imbalance occurs because women with PCOS have increased GnRH pulse frequency, which preferentially stimulates LH secretion over FSH. The elevated LH stimulates ovarian theca cells to produce excess androgens, particularly testosterone. Meanwhile, the relatively low FSH levels fail to adequately stimulate follicular development and aromatase activity, which would normally convert androgens to estrogens. This hormonal environment creates a self-perpetuating cycle where high androgens and insulin resistance (common in PCOS) further suppress FSH and enhance LH secretion. Additionally, the lack of regular ovulation prevents the normal cyclic changes in these hormones. The elevated LH:FSH ratio (often >2:1) is a characteristic finding in many PCOS patients and contributes to the clinical manifestations of the syndrome, including anovulation, polycystic ovaries, and hyperandrogenism, as supported by previous studies 1. Some key points to consider in PCOS management include:
- Insulin resistance plays a crucial role in the pathophysiology of PCOS, and lifestyle modifications can help improve symptoms 1
- The use of combination oral contraceptive pills can help suppress androgen secretion and increase sex hormone binding globulin levels 1
- Insulin-sensitizing agents, such as metformin, can improve insulin sensitivity and decrease circulating androgen levels 1
From the Research
Hormonal Imbalance in PCOS
- The hormonal imbalance in PCOS is characterized by an increased luteinizing hormone (LH) level and a decreased follicle-stimulating hormone (FSH) level, resulting in an elevated LH/FSH ratio 2, 3, 4.
- This imbalance is thought to be caused by an increased frequency of gonadotropin-releasing hormone (GnRH) secretion, which stimulates the release of LH from the pituitary gland 2.
- The decreased sensitivity to progesterone negative feedback on the GnRH pulse generator may also contribute to the increased LH/FSH ratio in PCOS 2.
- Additionally, chronic mild estrogen increases and inhibin may play a role in the low to normal FSH levels in PCOS 2.
Factors Influencing LH and FSH Levels
- The levels of LH and FSH in PCOS can be influenced by various factors, including the phase of the menstrual cycle 4.
- A study found that the reproducibility of elevated LH levels and LH/FSH ratio was poor in the early phase of the follicular phase, but improved in the late phase 4.
- Body mass index (BMI) does not appear to have a significant inverse relationship with LH levels in PCOS 4.
Clinical Implications
- The hormonal imbalance in PCOS can have significant clinical implications, including infertility and metabolic disorders 3.
- Treatment options for PCOS, such as ovulation induction with gonadotropins, may be effective in improving fertility outcomes, but the choice of treatment should be individualized based on the specific needs and circumstances of each patient 5, 6.