The endocrine role of the testicle:
Correct Answer: C
Rationale: The correct answer is C because the endocrine role of the testicle primarily involves the secretion of testosterone. Testosterone is the main androgenic hormone produced by the testicles, which plays a crucial role in various physiological functions such as the development of male reproductive organs, sperm production, and secondary sexual characteristics.
Choice A is incorrect because while interstitial cells (Leydig cells) are involved in the production of testosterone, the endocrine role of the testicle is not limited to these cells alone.
Choice B is incorrect as it is too general. While androgenic hormones are indeed secreted by the testicles, testosterone specifically is the main androgenic hormone produced by them.
Choice D is incorrect as the maturation of sex organs is primarily regulated by the action of testosterone but is not the sole endocrine role of the testicle.