Figure 1: Genetic control of pubertal development. Different levels of GnRH and gonadotropin deficiency due to genetic disorders. (1) Developmental defects of GnRH neurons due to disturbed neuronal migration and differentiation cause aplasia of GnRH neurons and olfactory tract. (2) Impaired GnRH synthesis or secretion is found in the context of functional disorders within the hypothalamus or the GnRH neuron itself. (3) GnRH resistance is caused by inactive GnRH receptor variants localised within the anterior pituitary gland. (4) Gonadotropin deficiency may be due to defect synthesis of LH or FSH β-subunits.