The testosterone levels in a man drop the cause of problem is probably hormone produced the?

The hormone produced is Luteinizing hormone (LH).

LH, also known as interstitial cell stimulating hormone (ICSH) in males, is a peptide hormone produced by gonadotropic cells in the anterior pituitary gland. In men, LH stimulates Leydig cells in the testes to produce testosterone, which is responsible for the development and maintenance of male reproductive tissues such as the testes and prostate gland, and for secondary sexual characteristics such as a deep voice and facial hair.