Thursday, January 24, 2013

Diabetic male with Erectile dysfunction and decreased libido

Clinical Vignette: A 36-year-old male with insulin-dependent diabetes mellitus of three years duration presented with decreased libido and erectile dysfunction since diagnosis. No abnormalities were noted on genital examination. Investigations revealed:

  • plasma testosterone 6.0 nmol/L (9 - 35)
  • plasma follicle stimulating hormone 1.0 u/L (1-8)

Which of the following investigations is most appropriate next step?
  1. autonomic function testing
  2. Doppler studies of penile artery
  3. Nerve conduction studies
  4. Serum ferritin
  5. Serum prolactin

Answer to clinical vignette|case: (4)

         This IDDM patient appears to have hypogonadotrophic hypogonadism (HH) as reflected by low testosterone and low FSH. The combination is compatible with a diagnosis of haemochromatosis and measuring ferritin would be a reasonable investigation.
         Haemochromatosis typically causes hypogonadotrophic hypogonadism as a consequence of the ferritin deposition within the pituitary rather than primary testicular dysfunction.
         Autonomic nerve dysfunction is one of the commoner causes of impotence in a diabetic but in this case is not the cause of his HH. For similar reasons, both nerve conduction studies and dopplers are irrelevant.
         Prolactin would be a sensible measurement but probably if you were looking to confirm a diagnosis that incorporates the diabetes as well, Ferritin would be the investigation of choice.