Which hormone is responsible for the development of secondary sexual characteristics in boys during puberty?

The hormone responsible for the development of secondary sexual characteristics in boys during puberty is testosterone.

Here are the steps that explain this process:

1. At the onset of puberty, the hypothalamus (a part of the brain) starts to produce gonadotropin-releasing hormone (GnRH).

2. GnRH stimulates the pituitary gland (another part of the brain) to produce and release luteinizing hormone (LH) and follicle-stimulating hormone (FSH).

3. LH stimulates the testes to produce testosterone.

4. Testosterone is the key hormone that triggers the development of secondary sexual characteristics in boys. These characteristics include the growth of facial and body hair, deepening of the voice, enlargement of the penis and testes, and the development of muscles.