Shows the normal hormonal control of puberty from the hypothalamus down to the testes or ovaries and their negative feedback mechanisms. The negative feedback control allows just the right amount of hormone to be released according to the needs of the body at that time. Shows the effect of the interruption of GnRH hormone release from the hypothalamus and the subsequent inability of the testes and ovaries to function correctly at puberty as seen in cases of<unk> /HH. In most cases of<unk> /HH the testes and ovaries are able to function correctly, but fail to do so because they have not had the correct hormonal signals. The structure of GNRH1(from ) The underlying cause of<unk>  or other forms of hypogonadotropic hypogonadism is a failure in the correct action of the hypothalamic hormone GnRH. The term isolated GnRH deficiency (IGD) has increasingly been used to describe this group of conditions as it highlights the primary cause of these conditions and distinguishes them from other conditions such as Klinefelter syndrome or Turner syndrome which share some similar symptoms but have a different etiology. The term hypogonadism describes a low level of circulating sex hormones; testosterone in males and oestrogen and progesterone in females. Hypogonadism can occur through a number of different mechanisms. The use of the term hypogonadotropic relates to the fact that the hypogonadism found in HH is caused by a disruption in the production of the gonadotropin hormones normally released by the anterior pituitary gland known as luteinising hormone (LH) and follicle stimulating hormone (FSH). Failure in GnRH activity can otherwise be due to the absence of the GnRH releasing neurons inside the hypothalamus. HH can occur as an isolated condition with just the LH and FSH production being affected or it can occur in combined pituitary deficiency conditions. In the first 10 weeks of normal embryonic development, the GnRH releasing neurons migrate from their original source in the nasal region and end up inside the hypothalamus. These neurons originate in an area of the developing head, the olfactory placode, that will give rise to the olfactory epithelium; they then pass through the cribriform plate, along with the fibres of the olfactory nerves, and into the rostral forebrain. From there they migrate to what will become the hypothalamus. Any problems with the development of the olfactory nerve fibres will prevent the progression of the GnRH releasing neurons towards the brain.
Kallmann syndrome
Klinefelter syndrome
Waldmann disease
Turner syndrome
Angelman syndrome
Hanhart syndrome
Parsonage–Turner syndrome
Gerstmann syndrome