What laboratory findings are indicative of Turner syndrome?

Turner syndrome is characterized by the partial or complete absence of one of the X chromosomes in females, leading to a variety of developmental and physiological issues. One of the key laboratory findings in Turner syndrome is the presence of increased luteinizing hormone (LH) and follicle-stimulating hormone (FSH) concentrations.

The increase in LH and FSH levels is due to the gonadal dysgenesis that occurs in Turner syndrome. Since the ovaries are typically underdeveloped or absent, there is a lack of estrogen and inhibin production. This lack of feedback inhibition results in elevated levels of LH and FSH as the hypothalamic-pituitary-gonadal axis tries to stimulate ovarian function. The high levels of these gonadotropins are indicative of primary ovarian insufficiency, which is a hallmark of Turner syndrome.

In contrast, other options suggest findings that would not align with the pathophysiology of Turner syndrome, such as low levels of LH and FSH, normal karyotype analysis, or elevated testosterone levels, none of which are consistent with the diagnosis. Therefore, the increased gonadotropin concentrations are a crucial laboratory finding in confirming Turner syndrome.