MLAB 2401: CLINICAL CHEMISTRY
KERI BROPHY-MARTINEZ
The 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 androgen
 DHEA: 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
–
–
–
•
Progesterone
–
•
Promotes breast, uterine and vaginal development
Secondary sex characteristics
Produced by placenta & ovaries
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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