What factors affect libido (Libido)?

A: Libido is an important factor in the formation and maintenance of intimate human relationships. Libido is affected by the following factors: 
- Change in levels of neurotransmitters such as testosterone, estrogen, progesterone... can change libido. 
- Psychological and social factors such as stress at work, fatigue, insomnia... can reduce Libido. 
- Health, disease and age: The decline in health and increasing age leads to the decline in Libido.