Hypothalamic-Pituitary-Gonadal Axis

Publisher Summary This chapter discusses tests for the diagnosis of disorders related to hypothalamic–pituitary–gonadal axis. Because the measurement of luteinizing hormone releasing hormone in peripheral blood is not available as a practical diagnostic procedure, the tests of hypothalamic function must rely on the assessment of gonadotropin or gonadal steroid responses. Absent responses can be because of either hypothalamic or pituitary disease. However, it must be pointed out that the measurement of baseline gonadotropin and gonadal steroid levels is usually sufficient to localize lesions for clinical management purposes. Thus, the finding of elevated gonadotropin levels (particularly follicle stimulating hormone) with low normal or low levels of testosterone or estradiol is evidence in favor of a primary gonadal disorder, while normal or low gonadotropin levels with low steroid concentrations point to a hypothalamic or pituitary lesion.