A boy is diagnosed

with a rare congenital Kallmann syndrome. This syndrome is characterized by anosmia

(absence of smell) and reduced or zero production of the gonadotropin-releasing

hormone GnRH, which leads to reduced production of the follicle-stimulating

hormone FSH and luteinizing hormone LH, and subsequently to delayed or no

puberty (pubertas tarda). Which cells are the normal source of FSH and LH?