The interstitial cells, which lie between the seminiferous tubules, produce testosterone.

These cells are activated during puberty by two hormones, FSH and LH, which is called interstitial cell stimulating hormone (ICSH). A rise in testosterone production in the young male stimulates his reproductive organs to develop to their adult size and causes secondary sex characteristics to appear.

These characteristics are:

a. Deepening of the voice due to enlargement of the larynx.

b. Increased hair growth especially on the face, axillary, and pubic regions.

c. Enlargement of skeletal muscles.

d. Increase in skeletal size.