Incomplete development of male secondary sexual characteristics is caused due to deficiency in Testosterone.

Testosterone is the primary male sex hormone that plays a crucial role in the development of male secondary sexual characteristics. These characteristics include the growth of facial and body hair, deepening of the voice, increased muscle mass and strength, and the development of the male reproductive organs.

Here is a detailed explanation of how the deficiency of testosterone can lead to incomplete development of male secondary sexual characteristics:

1. Testosterone and its role in sexual development:
- Testosterone is produced by the testes in males and is responsible for the development and maintenance of male sexual characteristics.
- During puberty, testosterone levels increase, leading to the development of secondary sexual characteristics.

2. Incomplete development of facial and body hair:
- Testosterone is responsible for the growth of facial and body hair in males.
- A deficiency in testosterone can result in insufficient hair growth or the absence of facial and body hair.

3. Lack of deepening of the voice:
- Testosterone promotes the growth and development of the larynx, which leads to a deepening of the voice in males.
- Inadequate levels of testosterone can prevent the larynx from fully developing, resulting in a higher-pitched voice.

4. Insufficient muscle mass and strength:
- Testosterone is an anabolic hormone that stimulates muscle growth and increases muscle mass and strength.
- A deficiency in testosterone can lead to reduced muscle development and weaker muscles.

5. Underdeveloped male reproductive organs:
- Testosterone is essential for the development and maturation of the male reproductive organs, including the penis and testes.
- Insufficient testosterone levels can result in the incomplete development of these organs.

In conclusion, testosterone is crucial for the development of male secondary sexual characteristics. A deficiency in testosterone can lead to incomplete development of facial and body hair, lack of deepening of the voice, insufficient muscle mass and strength, and underdeveloped male reproductive organs.