Which of the following hormone assays should the PCP order to determine if this man has low testosterone as a result of an impaired hypothalamic pituitary testicular axis? A 26 yo male visits his primary CARE physician (PCP). The man complains of lethargy and muscle weakness. He then explains to his PCP that he and his wife have been trying to get pregnant for the past 8 months with no success.¬† The man further explains that sometimes he is unable to maintain an erection, and because he can't match his wife's libido he is feeling depressed. His PCP suspects this man may have decreased levels of testosterone. \n
A. Testesterone and dehydrotestosterone B. Dehydrotestosterone and prolactin C. Testosterone and follicle stimulating hormone D. Luteinizing hormone and follicle stimulating hormone E. Testosterone and luteinizing hormone
Luteinizing hormone (LH) works directly on the interstitial cells of Leydig (i.e.
Leydig cells) to stimulate the production of testosterone. Low levels of LH can result in decreased levels of testosterone,
which can subsequently lead to decreased sperm production. Remember that LH acts directly on the Leydig cells, and
then the testosterone generated within the Leydig cells acts on the Sertoli cells to regulate spermatogenesis Prolonged
exposure to low levels of testosterone can also lead to systemic effects, such as decreased muscle mass and/or lethargy.
Evaluating the levels of DHT and FSH would also be beneficial, since levels of DHT are directly correlated with levels of
testosterone and FSH is also required by the Sertoli cells during the process of spermatogenesis. Additionally, checking
the levels of prolactin could be informative, since prolactin helps stimulate the expression of the LH receptors.
However, in this particular case the PCP suspects a problem with testosterone production and/or secretion, and
therefore the first step is to directly measure serum levels of testosterone and LH.