Occurs when the body doesn’t produce enough testosterone.

Types:

• Primary hypogonadism (testicular failure)
• Secondary hypogonadism (pituitary or hypothalamic dysfunction)

Causes:

• Klinefelter syndrome (XXY)
• Testicular injury, infection, or cancer
• Pituitary tumors, trauma, or surgery
• Aging, obesity, chronic illness

Symptoms (in males):

• Low libido
• Erectile dysfunction
• Fatigue, depression
• Reduced muscle mass
• Infertility
• Decreased facial/body hair

Usually due to:

• Testosterone therapy overdose
• Anabolic steroid abuse
• Androgen-producing tumors (adrenal or testicular)

Effects:

• Aggression, mood swings (“roid rage”)
• Acne, oily skin
• Male pattern baldness
• Testicular atrophy
• Infertility (due to feedback inhibition of LH/FSH)
• Gynecomastia (via estrogen conversion)

Cause:

• Genetic mutation in the androgen receptor
• Individuals with XY chromosomes are partially or completely insensitive to testosterone

Results:

• May present with female external genitalia despite XY chromosomes
• No uterus, no menstruation
• Undescended testes (in complete AIS)

Causes:

• Polycystic ovary syndrome (PCOS) – most common
• Congenital adrenal hyperplasia (CAH)
• Androgen-secreting tumors
• Cushing’s syndrome

Symptoms:

• Hirsutism (facial/body hair)
• Acne
• Male pattern hair loss
• Irregular or absent periods
• Infertility
• Deepened voice (in severe cases)

Testosterone Replacement Therapy (TRT) may be used in hypogonadism, but can lead to:

• Polycythemia (high RBC count)
• Sleep apnea worsening
• Prostate effects (concerns over benign hypertrophy or cancer risk)
• Suppressed fertility