What is hypogonadotropic hypogonadism?
A hypogonadotropic hypogonadism is a form of hypogonadism in which the production of the hormones LH (luteinizing hormone) and FSH (follicle-stimulating hormone) is reduced. As a result, the testes do not receive sufficient signals to produce testosterone and sperm.
The term is composed of the words hypo (reduced), gonadotrop (stimulating the gonads) and hypogonadism. It therefore refers to hypogonadism with too low gonadotropin levels.
In most cases, hypogonadotropic hypogonadism corresponds to a secondary hypogonadism, since the cause lies in the hypothalamus or in the pituitary gland. It can be congenital or develop over the course of life. The terms hypogonadotropic hypogonadism and secondary hypogonadism are often used similarly, but describe different aspects. Secondary hypogonadism refers to the location of the disorder in the hypothalamus or pituitary gland. Hypogonadotropic hypogonadism, on the other hand, describes the typical hormonal pattern with low or inappropriately normal LH and FSH levels in relation to low testosterone. In practice, both forms therefore usually occur together.
How does hypogonadotropic hypogonadism develop?
Testosterone production is controlled via the so-called HPG axis.
Normally, the hypothalamus produces the hormone GnRH, which stimulates the pituitary gland to release LH and FSH. These hormones then stimulate the testes to produce testosterone and sperm.
In hypogonadotropic hypogonadism, this feedback loop does not function sufficiently. Too little LH and FSH are produced, which reduces testosterone production in the testes.
Since the testes are often fundamentally functional, hormone production can return to normal in some cases after treating the cause.
What causes can hypogonadotropic hypogonadism have?
Hypogonadotropic hypogonadism can be congenital or acquired.
The most common causes include:
- congenital disorders of GnRH production, such as Kallmann syndrome
- pituitary gland diseases
- hypothalamus diseases
- pituitary tumors
- hyperprolactinemia
- traumatic brain injuries
- chronic diseases
- severe obesity
- chronic stress
- sleep deprivation
- certain medications, such as opioids or glucocorticoids
Functional hypogonadism resulting from obesity or metabolic disorders can also be associated with low gonadotropin levels.
What symptoms occur in hypogonadotropic hypogonadism?
The symptoms often correspond to those of a testosterone deficiency.
Typical symptoms are:
- reduced libido
- erectile dysfunction
- fatigue and exhaustion
- reduced muscle mass
- increased body fat
- reduced physical performance
- concentration problems
- depressive mood
- reduced beard growth
- fertility problems
In congenital forms, symptoms may become noticeable as early as puberty, when normal sexual development does not occur or is delayed.
How is hypogonadotropic hypogonadism diagnosed?
The diagnosis is made based on the symptoms, physical examination, and targeted hormone testing.
Typically, the following laboratory findings are observed:
- Total testosterone low
- Free testosterone low
- LH low or at the lower end of the normal range
- FSH low or at the lower end of the normal range
In addition, other laboratory values are often determined, including:
- SHBG
- Estradiol
- Prolactin
Depending on the findings, further examinations may be necessary, such as a magnetic resonance imaging (MRI) scan of the pituitary gland or genetic testing.
How does hypogonadotropic hypogonadism differ from hypergonadotropic hypogonadism?
The terms describe the concentration of the gonadotropins LH and FSH.
In hypogonadotropic hypogonadism, LH and FSH are low or inappropriately normal. The cause lies in the hypothalamus or pituitary gland.
In hypergonadotropic hypogonadism, on the other hand, LH and FSH are elevated. In this case, the functional disorder is directly in the testes, which produce too little testosterone despite increased hormonal stimulation.
The distinction is crucial for further diagnosis and therapy.
How is hypogonadotropic hypogonadism treated?
Treatment is based on the underlying cause.
If possible, the causative disease should first be treated or a modifiable risk factor reduced.
If there is a persistently low testosterone level with corresponding symptoms and there are no contraindications, testosterone replacement therapy (TRT) may be considered.
If the patient wishes to have children, other treatment methods are often used that can specifically stimulate the body's own production of LH, FSH, or testosterone.
Conclusion
Hypogonadotropic hypogonadism is a form of hypogonadism in which too little LH and FSH are produced due to a disorder of the hypothalamus or pituitary gland. As a result, the testes produce too little testosterone and often fewer sperm.
Careful hormone testing enables differentiation from other forms of hypogonadism and forms the basis for targeted treatment. An overview of signs and treatment is provided in our article Testosterone Deficiency in Men: Causes, Symptoms, and Solutions.