Understanding Gonadotrophins: The Role of LH and FSH in Reproductive Health

Gonadotrophins, namely luteinizing hormone (LH) and follicle-stimulating hormone (FSH), play a crucial role in reproductive health by regulating the function of the testes in men and the ovaries in women. In cases of primary testicular or ovarian failure, serum levels of these hormones can rise significantly. This overactivity is commonly physiological in women post-menopause, as the depletion of ovarian follicles leads to the cessation of cyclical hormone production.

Interestingly, while excessive gonadotrophin levels are rare due to increased stimulation from gonadotropin-releasing hormone (GnRH), there are conditions where inappropriate timing of hormone production can lead to disorders such as central precocious puberty. Conversely, pituitary adenomas that secrete functional LH or FSH are extremely rare. Non-functioning adenomas, while not secreting these hormones, may still show positive staining for the alpha-subunit, hinting at their developmental lineage.

During childhood, low levels of gonadotrophins are normal, but if this inactivity continues, it can delay puberty. A GnRH stimulation test can help assess this condition, measuring LH and FSH levels at intervals post-stimulation. A healthy response typically shows a two- to three-fold increase in hormone levels. However, after puberty, a loss of these gonadotrophins can lead to secondary hypogonadism, which is a common occurrence in women during various reproductive stages.

Multiple factors can contribute to changes in gonadotrophin levels. In women, stressors such as intense exercise, strict dieting, or emotional anxiety can significantly impact cyclical gonadotrophin secretion. Additionally, elevated prolactin levels can suppress LH and FSH production. Certain genetic syndromes, such as Kallman syndrome, result in the absence of GnRH-secreting neurons and lead to a lack of gonadotrophin production.

Clinically, it is essential to recognize that low gonadotrophin levels may be inappropriate in the context of hypogonadal symptoms and low sex hormone levels. In women, fluctuations in gonadotrophin levels throughout the menstrual cycle can complicate this diagnosis, often presenting as amenorrhea alongside low or undetectable serum estrogen. This condition is classified as hypogonadotropic hypogonadism, highlighting the complex interplay between these hormones and reproductive health. Understanding these mechanisms is vital for diagnosing and treating reproductive disorders effectively.