The male endocrine system is responsible for causing the testes to produce testosterone. The HPTA (hypothalamic-pituitary-testicular axis) regulates the level of testosterone in the bloodstream. And. The hypothalamus produces gonadotropin-releasing hormone (GnRH), which stimulates the pituitary gland to release Leutenizing hormone (LH). LH released by the pituitary gland then travels from the pituitary via the blood stream to the testes where it triggers the production and release of testosterone. Without the continuing release of LH by the pituitary gland, the testes would shut down their production of testosterone, causing testicular atrophy and stopping natural testosterone produced by the testes.