Hi Said,

Thanks for your query.

I believe your question is "what is reason for not getting the penis to become hard as it used to be ?"

This condition is called "Erectile dysfunction"

The causes are as follows:
With reduced libido (libido means urge to have to sex)
1. Hypogonadism
2. Depression
With intact libido
1. Psychological problems, including anxiety
2. Vascular insufficiency (atheroma)
3. Neuropathic causes (e.g. diabetes mellitus, alcohol excess, multiple sclerosis)
4. Drugs (e.g. β-blockers, thiazide diuretics)

90% of the patients who complains of this problem is mostly due to Psychological problems.

Treatment:
So the main stay of treatment is Psychotherapy, which includes the sexual partner is most useful for psychological problems.

If any underlying medical illness are found they should be treated first.

Other treatment options
1. Sildenafil (Viagra)
2. Self-administered intracavernosal injection or urethral gel administration of prostaglandin E1
3. Vacuum devices
4. Prosthetic implants

I hope my answer has been adequate and informative. If you have any follow up queries I will be available to answer them.

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