Endocrine Testicles Flashcards
What are the two main functions of the testicles?
- Endocrine function – Production of androgens (testosterone) for sexual development.
- Exocrine function – Production of spermatozoa (spermatogenesis).
Where does steroid hormone biosynthesis occur in the testicles?
In Leydig cells, which primarily produce testosterone.
What are the two main metabolic pathways of testosterone?
Testosterone → Dihydrotestosterone (DHT): More active androgenic form.
2. Testosterone → Δ4-Androstenedione: Inactive form, metabolized in the liver.
What are the physiological effects of androgens?
- Sexual Differentiation: Fetal development, puberty, libido.
- Trophic Effects: Muscle growth, bone mass increase, sebaceous gland regulation.
What is the Hypothalamic-Pituitary-Testicular Axis?
- GnRH (Gonadotropin-Releasing Hormone) → Stimulates release of LH & FSH.
- LH → Stimulates Leydig cells to produce testosterone.
- FSH → Regulates Sertoli cells, supporting spermatogenesis.
- Leydig Cells → Produce testosterone.
- Sertoli Cells → Support sperm development.
gland regulation.
What are the main static hormonal tests in testicular function?
- Testosterone Assay (dry tube sample).
- LH & FSH Assay – Evaluates pituitary gonadotropins.
- Δ4-Androstenedione Assay – Precursor to testosterone.
- 17-β Estradiol Assay – Detects gynecomastia, hyperestrogenism.
- Prolactin Assay – Related to hyperprolactinemia & infertility.
- Urinary 17-Ketosteroid Assay – Measures androgen metabolism.
What is the clinical significance of increased prolactin in males?
It suggests hyperprolactinemia, which can cause infertility & hypogonadism.
What is Δ4-Androstenedione and why is it measured?
It is a precursor to testosterone, and abnormalities may indicate enzyme deficiencies or androgen metabolism disorders.
What is 17-β Estradiol used for in male patients?
- Evaluates gynecomastia.
- Diagnoses hyperestrogenism in testicular tumors.
- Monitors abnormal hair growth patterns.
What is the Clomiphene Citrate Stimulation Test used for?
It stimulates GnRH secretion, measuring LH & FSH response to assess hypothalamic-pituitary function.
What is the GnRH Stimulation Test used for?
It differentiates between hypothalamic and pituitary dysfunction in hypogonadism
What is the hCG Testicular Stimulation Test used for?
- Mimics LH action on Leydig cells.
- Assesses peripheral hypogonadism.
- Used in cryptorchidism (undescended testes) & anorchidism (absent testes).
What is True Precocious Puberty, and what are its biochemical markers?
- Early activation of the hypothalamic-pituitary-gonadal axis.
- Elevated testosterone & LH/FSH.
What is Pseudo-Precocious Puberty, and what causes it?
- Excess adrenal androgens, leading to early puberty symptoms.
- Caused by congenital adrenal hyperplasia, adrenal tumors, or Cushing’s syndrome.
What are the causes of delayed puberty?
- Klinefelter Syndrome (47-XXY) – Testicular failure & infertility.
- Congenital Anorchidism – Absence of testicles.
- Androgen Resistance Syndrome – Defective androgen receptors.
What is Hypergonadotropic Hypogonadism, and what are its biochemical findings?
- Primary testicular failure → Elevated LH & FSH, low testosterone.
- Seen in Klinefelter Syndrome & testicular injury.
What is Hypogonadotropic Hypogonadism, and what are its causes?
- Central (pituitary/hypothalamic) dysfunction → Low LH, FSH, and testosterone.
- Causes: Kallmann syndrome (GnRH deficiency), pituitary tumors, chronic illness
What is Normogonadotropic Hypogonadism with Hyperprolactinemia?
- Normal LH/FSH, but high prolactin suppresses testosterone.
- Causes: Pituitary adenoma, medications, hypothyroidism.
What are three major enzyme deficiencies affecting testicular function?
- 17-Ketoreductase Deficiency – Prevents testosterone activation.
- 17-Ketohydroxylase Deficiency – Blocks steroidogenesis, leading to under-masculinization.
- 17,20-Desmolase Deficiency – Disrupts testosterone synthesis.
What hormonal tests should be done for a male with infertility?
- Testosterone (low in hypogonadism).
- LH/FSH (differentiates primary vs. secondary hypogonadism).
- Prolactin (elevated in hyperprolactinemia).
- Semen analysis (evaluates sperm production).
What biochemical findings suggest a testicular tumor?
- Elevated β-hCG (marker for germ cell tumors).
- Increased AFP (suggests non-seminomatous tumors).
- Increased 17-β estradiol (some tumors produce estrogen).
What laboratory findings are expected in Klinefelter Syndrome?
- Low testosterone.
- High LH & FSH (due to testicular failure).
- Gynecomastia (due to increased estradiol/testosterone ratio)
What test is essential to differentiate between primary and secondary hypogonadism?
GnRH Stimulation Test – Determines if the dysfunction is pituitary or hypothalamic.
A patient has gynecomastia and low testosterone. What test should be ordered?
17-β Estradiol Assay – To check for hyperestrogenism.
