Endocrine Testicles Flashcards

1
Q

What are the two main functions of the testicles?

A
  1. Endocrine function – Production of androgens (testosterone) for sexual development.
  2. Exocrine function – Production of spermatozoa (spermatogenesis).
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2
Q

Where does steroid hormone biosynthesis occur in the testicles?

A

In Leydig cells, which primarily produce testosterone.

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3
Q

What are the two main metabolic pathways of testosterone?

A

Testosterone → Dihydrotestosterone (DHT): More active androgenic form.
2. Testosterone → Δ4-Androstenedione: Inactive form, metabolized in the liver.

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4
Q

What are the physiological effects of androgens?

A
  • Sexual Differentiation: Fetal development, puberty, libido.
  • Trophic Effects: Muscle growth, bone mass increase, sebaceous gland regulation.
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5
Q

What is the Hypothalamic-Pituitary-Testicular Axis?

A
  • 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.
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6
Q

What are the main static hormonal tests in testicular function?

A
  1. Testosterone Assay (dry tube sample).
  2. LH & FSH Assay – Evaluates pituitary gonadotropins.
  3. Δ4-Androstenedione Assay – Precursor to testosterone.
  4. 17-β Estradiol Assay – Detects gynecomastia, hyperestrogenism.
  5. Prolactin Assay – Related to hyperprolactinemia & infertility.
  6. Urinary 17-Ketosteroid Assay – Measures androgen metabolism.
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7
Q

What is the clinical significance of increased prolactin in males?

A

It suggests hyperprolactinemia, which can cause infertility & hypogonadism.

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8
Q

What is Δ4-Androstenedione and why is it measured?

A

It is a precursor to testosterone, and abnormalities may indicate enzyme deficiencies or androgen metabolism disorders.

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9
Q

What is 17-β Estradiol used for in male patients?

A
  • Evaluates gynecomastia.
  • Diagnoses hyperestrogenism in testicular tumors.
  • Monitors abnormal hair growth patterns.
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10
Q

What is the Clomiphene Citrate Stimulation Test used for?

A

It stimulates GnRH secretion, measuring LH & FSH response to assess hypothalamic-pituitary function.

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11
Q

What is the GnRH Stimulation Test used for?

A

It differentiates between hypothalamic and pituitary dysfunction in hypogonadism

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12
Q

What is the hCG Testicular Stimulation Test used for?

A
  • Mimics LH action on Leydig cells.
  • Assesses peripheral hypogonadism.
  • Used in cryptorchidism (undescended testes) & anorchidism (absent testes).
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13
Q

What is True Precocious Puberty, and what are its biochemical markers?

A
  • Early activation of the hypothalamic-pituitary-gonadal axis.
  • Elevated testosterone & LH/FSH.
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14
Q

What is Pseudo-Precocious Puberty, and what causes it?

A
  • Excess adrenal androgens, leading to early puberty symptoms.
  • Caused by congenital adrenal hyperplasia, adrenal tumors, or Cushing’s syndrome.
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15
Q

What are the causes of delayed puberty?

A
  1. Klinefelter Syndrome (47-XXY) – Testicular failure & infertility.
  2. Congenital Anorchidism – Absence of testicles.
  3. Androgen Resistance Syndrome – Defective androgen receptors.
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16
Q

What is Hypergonadotropic Hypogonadism, and what are its biochemical findings?

A
  • Primary testicular failure → Elevated LH & FSH, low testosterone.
  • Seen in Klinefelter Syndrome & testicular injury.
17
Q

What is Hypogonadotropic Hypogonadism, and what are its causes?

A
  • Central (pituitary/hypothalamic) dysfunction → Low LH, FSH, and testosterone.
  • Causes: Kallmann syndrome (GnRH deficiency), pituitary tumors, chronic illness
18
Q

What is Normogonadotropic Hypogonadism with Hyperprolactinemia?

A
  • Normal LH/FSH, but high prolactin suppresses testosterone.
  • Causes: Pituitary adenoma, medications, hypothyroidism.
19
Q

What are three major enzyme deficiencies affecting testicular function?

A
  1. 17-Ketoreductase Deficiency – Prevents testosterone activation.
  2. 17-Ketohydroxylase Deficiency – Blocks steroidogenesis, leading to under-masculinization.
  3. 17,20-Desmolase Deficiency – Disrupts testosterone synthesis.
20
Q

What hormonal tests should be done for a male with infertility?

A
  • Testosterone (low in hypogonadism).
  • LH/FSH (differentiates primary vs. secondary hypogonadism).
  • Prolactin (elevated in hyperprolactinemia).
  • Semen analysis (evaluates sperm production).
21
Q

What biochemical findings suggest a testicular tumor?

A
  • Elevated β-hCG (marker for germ cell tumors).
  • Increased AFP (suggests non-seminomatous tumors).
  • Increased 17-β estradiol (some tumors produce estrogen).
22
Q

What laboratory findings are expected in Klinefelter Syndrome?

A
  • Low testosterone.
  • High LH & FSH (due to testicular failure).
  • Gynecomastia (due to increased estradiol/testosterone ratio)
23
Q

What test is essential to differentiate between primary and secondary hypogonadism?

A

GnRH Stimulation Test – Determines if the dysfunction is pituitary or hypothalamic.

24
Q

A patient has gynecomastia and low testosterone. What test should be ordered?

A

17-β Estradiol Assay – To check for hyperestrogenism.

25
Q

A child has delayed puberty and low testosterone. What is the next step?

A

GnRH Stimulation Test – To determine if the cause is hypothalamic or pituitary.