Excess testosterone can occur due to conditions like polycystic ovarian syndrome (PCOS), adrenal tumors, or exogenous steroid use. In males, high testosterone levels may not have noticeable effects. In females, it can lead to clitoromegaly, acne, hirsutism, menstrual irregularities, and male-pattern baldness. Excess testosterone can also have toxic effects, including over-masculinization, decreased menses, acne, and clitoral enlargement.