A 30 year old male complains of loss of erection with low testosterone and high prolactin level in blood. What is likely diagnosis -

Ans. is 'a' Pituitary adenoma .Loss of erection with low testosterone level and increased prolactin level strongly suggests the diagnosis of prolactin secreting pituitary adenoma.These tumors arise from lactotroph cells and secrete prolactin. The low testosterone level can be attributed to gonadotropin suppression by the pituitary tumour.Presenting features in case of prolactinoma are -Loss of libidoVisual loss (due to optic nerve compression)Now let's see other options :Craniopharyngioma : Craniopharyngioma never affects prolactin level. The only hormone affected in craniopharyngioma is ADH. It causes Diabetes insipidus (d/t decreased ADH).Testicular failure will lead to decreased Testosterone but there will be no effect on prolactin. Moreover gonadotropin level will be increased whereas in prolactinoma gonadotropins are decreased.Cushing's syndrome : There will be no effect on either testosterone or prolactin level.