Clinical Chemistry Week 11

What is the most common pituitary tumor?

Prolactin-secreting tumors

What percentage of people harbor clinically silent pituitary tumors?

20%

What zone of the adrenal gland synthesizes aldosterone?

Zona glomerulosa

What zone of the adrenal gland synthesizes glucocorticoids?

Zona fasciculata

What zone of the adrenal gland secretes mineralocorticoids, adrenal androgens, and estrogens?

Zona reticularis

What are the main adrenal androgens?

DHEA and DHEA-S

What else does the zona glomerulosa do?

It is critical for sodium retention, potassium excretion, acid-base balance, and blood pressure regulation

What system controls the release of aldosterone?

renin-angiotensin-aldosterone system (RAAS)

What else does the zona fasciculata do?

It is critical for glucose homeostasis and blood pressure

What hormones are produced by the hypothalamus?

• Growth hormone releasing hormones (GHRH)

• Corticotropin-releasing hormone (CRH)

• Tyrotropin releasing hormone (TRH)

• Gonadotroping releasing hormone (GnRH)

• Somatostatin

• Dopamine

• Arginine vasopressin

What does TRH stimulate?

Secretion of TSH and prolactin

What does GnRH stimulate?

Production of LH and FSH

What does somatistatin inhibit?

Inhibits GH and TSH release from the pituitary

What are the anterior pituritary hormones?

• LH

• FSH

• TSH

• ACTH

• Growth hormone

• Prolactin

What are tropic hormones?

Actions of hormones stimulate other endocrine glands to release hormones (indirect)

What anterior pituitary hormones are tropic hormones?

• TSH

• LH

• FSH

• ACTH

What does TSh promote?

Promotes thyroid hormone production from the thyroid

What does LH do?

Directs ovulation in women and testosterone production in men

What does FSH do?

Responsible for ovarian recruitment and early folliculogenesis in women and spermatogenesis in men

What does ACTH do?

Regulates adrenal steroidogenesis

What are direct effector hormones?

Act directly on target tissue

WHat anterior pituitary hormones are direct effector hormones?

• Growth hormone

• Prolactin

What is growth hormone?

Peptide hormone released from the anterior pituitary gland that controls growth and metabolism

What are somatotrophs?

pituitary cells that produce GH

What stimulates growth hormone and what inhibits growth hormone?

• GHRH- stimulates

• Somatostatin- inhibits

What is the reference range for GH in males?

0.01-1.0 ng/mL

What is the reference range for GH in females?

0.01-3.5 ng/mL

Which part of the pituitary gland produces and releases hormones under the regulation of the hypothalamus?

Anterior pituitary

Intermediate lobe

Frontal lobe

Posterior pituitary

Anterior pituitary

Which of the following is not a hormone produced by the hypothalamus?

Gonadotropin-releasing hormone

Growth hormone

Somatostatin

Corticotropin-releasing hormone

growth hormone

Low AVP levels and elevated plasma osmolality is indicative of

dwarfism

Addison's disease

prolactinoma

diabetes insipidus

diabetes insipidus

Which of the following is the most common type of functional pituitary tumor?

ACTH-secreting

GH-secreting

Prolactin-secreting

TSH-secreting

prolactin-secreting

The adrenal gland has an impact on all of the following except

blood pressure

androgen excess

acid-base balance

electrolyte balance

acid-base balance

DHEA-S, cortisol, and aldosterone are all major

adrenal cortical hormones

catecholamines

androgen hormones

all of the above

adrenal cortical hormones

Cortisol is synthesized in which adrenal cortex zone?

zona glomerulosa

zona fasciculata

zona reticularis

zona fasciculata

Angiotensin II stimulates the release of

cortisol

aldosterone

renin

ACTH

aldosterone

Which gland is affected in secondary adrenal insufficiency?

Hypothalamus

Kidneys

Pituitary

Adrenal

pituitary

A diagnosis of primary adrenal insufficiency requires demonstration of

decreased urinary 17-keto and 17-hydroxysteroids

decreased cortisol production

impaired response to ACTH stimulation

increased urinary cortisol excretion after metyrapone

impaired response to ACTH stimulation

24-hour free cortisol, midnight salivary cortisol, and dexamethasone suppression tests are done to help diagnose which condition?

Cushing's syndrome

Hypogonadism

Gonadal hyperandrogenism

Graves' disease

Cushing’s syndrome

If the dexamethasone suppression test produces a decreased cortisol level, that would indicate

a normal result

Addison's disease

Cushing's disease

Hypoaldosteronism

a normal result

Which test is the most specific and sensitive to test for adrenal hyperfunction?

24-hour urine free cortisol

Dexamethasone suppression

ACTH stimulation

Angiotensin II activity

24-hour urine free cortisol

Which amino acid does the adrenal medulla produce catecholamines?

Leucine

Tyrosine

Valine

Lysine

tyrosine

Catecholamines regulate the body's response to

glucose concentration

water retention

acid-base balance

stress

stress

Metanephrines are measured when which condition is suspected?

Cushing's disease

Pheochromocytoma

Adrenal incidentaloma

Hypercortisolism

pheochromocytoma

Which endocrine gland stimulates the secretion of pituitary hormones?

Posterior pituitary gland

Anterior pituitary gland

Hypothalamus

Pineal gland

hypothalamus

A growth hormone-secreting tumor in an adult may result in which of the following conditions?

Acromegaly

Cretinism

Gigantism

Dwarfism

acromegaly

What common precursor is used in the biosynthesis of adrenal steroids, including androgens and estrogens?

Cortisol

Catecholamines

Progesterone

Cholesterol

cholesterol

Which of the following sample collection would give an accurate assessment of potential excess cortisol production (hypercortisolism)?

Collect a plasma sample as a baseline, and another 1 hour after administration of metyrapone

Collect a plasma sample at 8 a.m. only

Collect a 24-hour urine free cortisol

Collect a plasma sample at 8 a.m. and at 8 a.m. the next day

Collect a 24-hour urine free cortisol

Aldosterone is released by the adrenal cortex upon stimulation by

renin

angiotensinogen

angiotensin I

angiotensin II

angiotensin II

An ACTH stimulation test is performed on a patient. After the synthetic ACTH levels were given, cortisol levels were drawn at 30 and 60 minutes. If the cortisol levels showed no change or a slight increase in cortisol, what would the diagnosis be?

Cushing's syndrome

Cushing's disease

Hyperaldosteronism

Addison's disease

Addison’s disease

The urinary excretion product measured as an indicator of epinephrine production is

dopamine

dihydroxyphenylalanine (DOPA)

homovanillic acid

vanillylmandelic acid (VMA)

vanillylmandelic acid (VMA)

The adrenal medulla secretes which of the following in the greatest quantity?

Metanephrine

Norepinephrine

Epinephrine

Dopamine

epinephrine

What regulates prolactin release from the pituitary?

dopamine

Prolactin inhibitory factor

Substance that controls amount of prolactin released from hypothalamus

What are the prolactin levels when prolactinoma is suspected?

>150 ng/mL

What is the reference range of prolactin?

males: 4.0-15.2 ng/mL

Females: 4.8-23.3 ng/mL

Hypopituitarism

failure of either pituitary or hypothalamus results in loss of anterior pituitary function

Panhypopituitarism

complete loss of function of pituitary

Monotropic hormone deficiency

loss of only a single pituitary hormone

When should you suspect hyperaldosteronism?

hypertension, hypokalemia, metabolic alkalosis

When should you suspect pheochromocytoma?

hypertension, spells of anxiety, palpatations, dizziness, and diaphoresis

When should you suspect cushings syndrome?

hypertension, rapid unexplained weight gain, red/purple stretch marks, proximal muscle weakness

When should you suspect primary adrenal insufficiency?

loss of appetite, unintentional weight loss, and pigment skin

WHat is primary adrenal insufficiency?

inadequate release of glucocorticoids, mineralcorticoids, and adrenal androgens despite adequate stimulation

WHat is the most common cause of primary adrenal insufficiency?

Autoimmune destruction/Addisons disease

What is the testing used to determine adrenal insufficiency?

Cortisol secretion. 1 sample drawn between 6-8 am and one taken at midnight.

Peak (6-8am): 7-25 micrograms/dL

Trough (midnight): 2-14 micrograms/dL

When is adrenal insufficiency suspected?

8:00 am cortisol is decreased, ACTH is increased

What test is used for diagnosis of adrenal insufficency?

ACTH stimulation test. Baselines are obtained, then synthetic ACTH is given. If no change in cortisol, diagnosis can be made

WHat is vanillymandelic acid?

When COMT and MAO produce metanephrines and normetanephrines that are then converted into this product. It is used to measure epinephrine production

What is COMT?

catecholamine-O-methyltransferase

What is MAO?

Monoamine oxidase

What are MAO and COMT?

enzymes that degrade free catecholamines

What is urine free cortisol?

• Most sensitive and specific test for adrenal hyperfunction

• Cortisol 3x above normal- cortisol excess

What is overnight dexamethasone suppression test?

• used if adrenal node or mass is found

• Administration of 1 mg dexamethasone with 8am cortisol level

• Negative is cortisol <1.8micrograms/dL

WHat is late night salivary cortisol level?

Excess endogenous production of cortisol loses diurnal variability, increased LNSC

What test is performed once hypercortisolism is established?

Sandwich electrochemiluminescence immunoassay for ACTH

What does it mean is 8 am ACTH is >15 micrograms/dL

cortisol secretion is considered ACTH dependent

What does it mean when 8am ACTH <5 micrograms/dL

cortisol secretion is considered ACTH independent

What does hyperaldosteronism result in?

hypertension, hypokalemia, metabolic alkalosis, increased risk of vascular disease

What are lab results seen in hyperaldosteronism?

Increased aldosterone, increased Na+, decreased K+