MLAB 2401: Clinical Chemistry Keri Brophy-Martinez

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MLAB 2401 Clinical ChemistryKeri Brophy-Martinez

• The Adrenals An Overview

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Adrenals

• Pyramid-shaped, located just above medial to
  kidneys
• Glands are about the size of a grape
• Produces both steroid hormones from cholesterol
  and other non-steroid hormones
• Conditions affect blood pressure electrolyte
  balance.
• Hypofunction is treated with exogenous hormone
  replacement, hyperfunction with pharmacologic
  suppression or surgery.

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Adrenal anatomy

• Three domains
• Capsule
• Cortex
• Consist of Endocrine tissue
• Medulla
• Consists of neurosecretory tissue

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Adrenal Microscopic Anatomy

• Zona Glomerulosa
• outer 10
• Synthesize mineralocorticoids
• Zona Fasciculata
• middle 75
• Synthesize glucocorticoids
• Zona Reticularis
• inner 10
• Secrete gonadocorticoids (androgens)
• Adrenal Medulla
• catecholamines

Sunheimer, R., Graves, L. (2010). Clinical
Laboratory Chemistry. Upper Saddle River Pearson
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Classes of Adrenal Cortex hormones

• Mineralocorticoids
• Regulate electrolytes
• Critical for sodium retention, potassium,
  acidbase homeostasis
• Aldosterone
• Controlled by the renin-angiotensin-aldosterone
  system
• Promotes potassium secretion
• Increases plasma sodium
• Increases water retention

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Classes of Adrenal Cortex Hormones

• Glucocorticoids
• Involved with metabolism of protein, and minerals
• Enhances fat lipolysis
• Involved with gluconeogenesis and glucose
  homeostasis
• Critical to blood pressure
• Plays a role in suppression of inflammatory and
  allergic reactions

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Glucocorticoids

• Cortisol- principle member
• Functions
• Acts be penetrating cell nucleus, binding DNA,
  and altering the transcription of RNA
• Insulin antagonist
• Primarily circulates bound to a protein
• Breaks down muscle proteins with enzymes
• Mobilizes fat for energy purposes
• Lessens immune response by inhibiting antibody
  formation

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Cortisol Regulation

• Hypothalamus secretes CRH (Corticotropin-
  releasing hormone)
• CRH activates adrenocorticotropic hormone (ACTH)
  in the anterior pituitary
• ACTH controls cortisol production
• Low levels of cortisol, promote ACTH release
• Elevated levels of cortisol, inhibit ACTH release

Sunheimer, R., Graves, L. (2010). Clinical
Laboratory Chemistry. Upper Saddle River Pearson
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Cortisol Testing

• Normal plasma concentration follows diurnal
  variation
• Fluctuates between 6-25 µg/dL
• Cortisol is conjugated and excreted in the urine
  as 17-hydroxycorticosteroids (17-OHCS)

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Classes of Adrenal Cortex Hormones

• Gonadocorticoids
• Androgens
• Testosterone is the principal androgen
• DHEA dehydroepiandrosterone

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Testes

• Function
• Produce sperm
• Production of reproductive steroid hormones
• Testosterone
• Maintains secondary sex characteristics and sperm
  production
• Principle androgen in the blood
• 95 bound to albumin/sex hormone binding protein

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Hormonal Control of Testicular Function

• Hypothalamus generates GNRH in a pulse-like
  fashion
• GNRH is released into the system
• GNRH determines the rate of production of LH and
  FSH
• FSH and LH activate testosterone production
• Testosterone converted to dihydrotestosterone to
  effect protein synthesis and cell growth

Sunheimer, R., Graves, L. (2010). Clinical
Laboratory Chemistry. Upper Saddle River Pearson
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Ovaries

• Function
• Ovum production
• Steroid hormone production
• Hormone Production
• Requires cholesterol

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Hormonal Control of Ovulation

• GNRH controls FSH and LH secretion
• During reproductive years, FSH increases in
  follicular phase of menses and LH surges
  mid-cycle to cause ovulation. Following
  ovulation, FSH decreases

Sunheimer, R., Graves, L. (2010). Clinical
Laboratory Chemistry. Upper Saddle River Pearson
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Female Sex Hormones

• Estrogens
• Includes estradiol, estrone, and estriol
• Promotes breast, uterine and vaginal development
• Secondary sex characteristics
• Produced by placenta ovaries
• Progesterone
• Prepares endometrium for implantation
• Androgens
• Testosterone DHEA (dehydroepiandrosterone)
• Promote development of masculine characteristics

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Placental hormones

• hCG Human Chorionic gonadotropin
• Composed of two subunits alpha beta
• Classic hormone marker of pregnancy
• Human placental lactogen
• Aids hCG in estrogen progesterone synthesis
• Promotes mammary gland development
• Progesterone
• Promotes growth and thickening of mucosal cells
• Ensures adequate uterine blood supply

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Adrenal Medulla Hormones

• Produced in small amounts and extremely potent,
  rapidly inactivated
• Mobilize energy stores and prepares body for
  muscular activity
• Released into the bloodstream during stress
• Catecholamines
• Nonsteroid, amine-type hormone

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Catecholamine Members

• Norepinephrine/ Noradrenaline
• Synthesized in the CNS
• Epinephrine/Adrenaline
• Produced by adrenal gland
• Increases blood glucose via breakdown of glycogen
• Increases heart rate and blood pressure
• Causes sweating and dilation of the eyes
• Dopamine

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Metabolism of catecholamines
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Importance of VMA HVA

• Pheochromocytoma
• Benign or malignant tumors in the adrenal medulla
• Causes hypertension
• Neuroblastoma/Ganlioneuromas
• Common malignant tumors in pediatric patients
• Elevations of VMA or HVA

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References

• Bishop, M., Fody, E., Schoeff, l. (2010).
  Clinical Chemistry Techniques, principles,
  Correlations. Baltimore Wolters Kluwer
  Lippincott Williams Wilkins.
• Sunheimer, R., Graves, L. (2010). Clinical
  Laboratory Chemistry. Upper Saddle River Pearson
  .