MLAB 2401: CLINICAL CHEMISTRYKERI BROPHY-MARTINEZThe Adrenals: An Overview

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.

ADRENAL ANATOMY

Three domains Capsule Cortex

Consist of Endocrine tissue

Medulla Consists of

neurosecretory tissue

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

CLASSES OF ADRENAL CORTEX HORMONES

Mineralocorticoids Regulate electrolytes

Critical for sodium retention, potassium, & acid–base homeostasis

Aldosterone Controlled by the renin-angiotensin-aldosterone

system Promotes potassium secretion Increases plasma sodium Increases water retention

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

GLUCOCORTICOIDS

Cortisol- principle member Functions

Acts by 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

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

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)

CLASSES OF ADRENAL CORTEX HORMONES

Gonadocorticoids Androgens

Testosterone is the principal androgenDHEA: dehydroepiandrosterone

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

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

OVARIES

Function Ovum production Steroid hormone production

Hormone Production Requires cholesterol

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

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

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

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

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

METABOLISM OF CATECHOLAMINES

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

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 .

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