For male differentiation to occur during embryonic development, testosterone must be secreted from the testes. What stimulates the secretion of testosterone during embryonic development?
**Core Concept**
The process of male differentiation during embryonic development is a complex series of events involving the secretion of testosterone from the testes. This process is initiated by the presence of the SRY gene, which triggers the development of testicular tissue. The Leydig cells within the testes then produce testosterone, a key hormone responsible for male sex differentiation.
**Why the Correct Answer is Right**
Testosterone secretion during embryonic development is stimulated by the Leydig cells, which are activated by the presence of luteinizing hormone (LH) from the pituitary gland. LH binds to its receptor on the Leydig cells, triggering the production of testosterone through the activity of the enzyme desmolase, which converts cholesterol into pregnenolone. Pregnenolone is then converted into androgens, including testosterone, through a series of enzyme-catalyzed reactions.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because LH is the primary hormone responsible for stimulating testosterone secretion in the testes, not FSH (Follicle-Stimulating Hormone). Although FSH does play a role in the development of the testes, it is not directly involved in testosterone production.
**Option B:** This option is incorrect because the presence of the Y chromosome is necessary for the initial development of testicular tissue, but it is not directly responsible for stimulating testosterone secretion.
**Option C:** This option is incorrect because the SRY gene is involved in the initial development of testicular tissue, but it does not directly stimulate testosterone secretion.
**Clinical Pearl / High-Yield Fact**
The Leydig cells of the testes are responsible for producing testosterone during embryonic development, which is essential for male sex differentiation. This process is initiated by the presence of the SRY gene and the subsequent activation of the Leydig cells by LH from the pituitary gland.
**Correct Answer:** C. The presence of the Leydig cells, which are activated by LH from the pituitary gland, stimulates the secretion of testosterone during embryonic development.