The Collaborative International Dictionary of English v.0.48:

LH \LH\ n. (Biochem.)
   An abbreviation for luteinizing hormone, a gonadotropic
   hormone that is secreted by the pituitary and stimulates
   ovulation in female mammals, and stimulates androgen release
   in male mammals. [Acronym]

   Syn: luteinizing hormone, interstitial cell-stimulating
        hormone.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

LH
    n 1: a gonadotropic hormone that is secreted by the anterior
         pituitary; stimulates ovulation in female mammals and
         stimulates androgen release in male mammals [syn:
         luteinizing hormone, LH, interstitial cell-stimulating
         hormone, ICSH]