Serum levels of follicle-stimulating hormone (FSH) and testosterone (T) are measured as part of a basic endocrine examination (FSH). Seminiferous epithelium may be roughly determined by serum FSH levels. Inhibin, a Sertoli cell product that normally feeds back to the pituitary and hypothalamus to cut off FSH secretion, is secreted insufficiently, leading to elevated blood FSH levels. This implies problems in the seminiferous epithelium, which in turn leads to aberrant spermatogenesis. The synthesis of Testosterone is stimulated by luteinizing hormone (LH), which also affects Leydig cells.