20) Endocrine Flashcards by Samantha Boyer

3 major classes of hormones

Polypeptide hormones
Steroid hormones
Hormones derived from
amino acids

How well did you know this?

Not at all

Perfectly

polypeptide hormone half-life is usually…

short (<30 min)

How well did you know this?

Not at all

Perfectly

affect targets via second messenger system

polypeptide hormones
amino acid based hormones

How well did you know this?

Not at all

Perfectly

steroid hormones are derived from…

cholesterol

How well did you know this?

Not at all

Perfectly

basic carbon skeleton structure for steroid hormones

cyclopentaoperhydrophenanthrene

How well did you know this?

Not at all

Perfectly

half-life of steroid hormones

30-90 min

How well did you know this?

Not at all

Perfectly

forms of circulating steroid hormones

bound to carrier proteins
unbound; able to promote physiological response

How well did you know this?

Not at all

Perfectly

examples of steroid hormones

Aldosterone
Cortisol
Estradiol (E2)
Progesterone
Testosterone

How well did you know this?

Not at all

Perfectly

hormones derived from tyrosine

T3
T4
epinephrine
norepinephrine

How well did you know this?

Not at all

Perfectly

hormones derived from tryptophan

melatonin
serotonin

How well did you know this?

Not at all

Perfectly

T4 half-life

7-10 days

How well did you know this?

Not at all

Perfectly

free catecholamine half-life

<1 min

How well did you know this?

Not at all

Perfectly

hormones derived from amino acids

Dopamine
Epinephrine (also adrenaline)
Norepinephrine (noradrenalin)
Serotonin
Thyroxine (T4)
Triiodothyronine (T3)

How well did you know this?

Not at all

Perfectly

act on endocrine glands to release their hormones

tropic hormones

How well did you know this?

Not at all

Perfectly

act on endocrine tissue to promote growth and function

trophic hormones

How well did you know this?

Not at all

Perfectly

2 major classes of hormone receptors

membrane (protein hormones; 2nd messenger)
nuclear (steroid & thyroid hormones)

How well did you know this?

Not at all

Perfectly

releasing factor

peptide synthesized by the hypothalamus and released into the portal circulation to affect pituitary hormone synthesis and secretion

How well did you know this?

Not at all

Perfectly

affects hypothalamus release of releasing factor

levels of circulating target hormone

How well did you know this?

Not at all

Perfectly

cortisol negative feedback

corticotrophin-releasing hormone (CRH) - hypothalamus
ACHT - anterior pituitary

How well did you know this?

Not at all

Perfectly

thyroid hormone negative feedback

thyrotrophin-releasing hormone (TRH) - hypothalamus
TSH - anterior pituitary

How well did you know this?

Not at all

Perfectly

gonadal steroids negative feedback

gonadotropin-releasing hormone (GnRH) - hypothalamus
FSH, LH - anterior pituitary

How well did you know this?

Not at all

Perfectly

2 types of assays for measuring hormones

competitive immunoassays: Ag competes with hormone for sites; hormone-Ag complex forms, inversely proportional to hormone level
immunometric assays: Ab used to “sandwich” hormone; complex is directly proportional to hormone level

How well did you know this?

Not at all

Perfectly

8pm ——– is approximately 50% of 8am levels

cortisol

How well did you know this?

Not at all

Perfectly

autonomy

syndromes of hormone excess (tumors)
overproduction is not suppressed by feedback

How well did you know this?

Not at all

Perfectly

examples of protein-bound hormones in circulation

cortisol T4

heterogeneity

hormones that circulate in blood as multiple distinct immunologic forms | ex) PTH

tropic hormone and target hormone both increased or decreased

secondary hyper/hypofunction **tropic hormone is first cause**

tropic hormone and target hormone in opposite directions

primary hyper/hypofunction **target hormone is first cause**

standard low levels of activity during total rest sufficient for dx when disease is **severe**

basal levels

stimulation or suppression tests are required when...

excess or deficiency is not severe/definitive

used to document hyposecretion explain

stimulation tests challenge with tropic hormone, determine if target hormone increases

used to document hypersecretion explain

suppression tests synthetic target hormone is given, determine if tropic hormone decreases

hormones of posterior pituitary

ADH oxytocin

hormones of anterior pituitary

ACTH FSH LH GH Prolactin TSH

AKA somatotropin

Gh functions

promote growth, cause changes in electrolyte metabolism, stimulate uptake of nonesterified fatty acids by muscle, and accelerates fat mobilization from adipose tissue

secretion is pulsatile, with greatest levels at night (onset of sleep)

Diagnosis of deficiency is usually made by provocative stimuli. (Exercise, insulin-induced hypoglycemia, and other pharmacologic tests that increase hormone)

Most validated test to distinguish pituitary-sufficient patients from those with adult GH deficiency

insulin-induced hypoglycemia stimulation test

acromegaly characteristics (4)

middle-aged pts elongation and enlargement of bones somatotrope adenomas cosecretion of prolactin

pituitary gigantism characteristics (3)

children elevated GH before long bones are finished growing linear growth

produced by lactotrophs of pituitary

prolactin

function of prolactin

initiate and sustain lactation control of osmolality, fat and carbohydrate metabolism, calcium and vitamin D metabolism, fetal lung development, and steroidogenesis

levels are controlled by dopamine, which inhibits it; if dopamine is absent, levels rise

prolactin

sensitive indicator of pituitary disease; first to rise during pituitary infiltrative disease/compression

prolactin

Anovulation (infertility) Amenorrhea and galactorrhea Galactorrhea alone Oligospermia or impotence in males

hyperprolactinemia

function of ADH

maintaining water homeostasis and electrolyte balance retain water, increase BP

functions of oxytocin

Stimulates the contraction of the estrogen-primed uterus (positive feedback) Also stimulates the lactating mammary gland Role in mother-infant bonding

Useful as a therapeutic agent in inducing labor

pitocin

2 types of DI

central nephrogenic

suspected if urine osmo > plasma osmo without increased urine Na

SIADH

areas of adrenal gland and hormones produced (4)

Outermost layer (zona glomerulosa)--Produces aldosterone Broad lipid-filled (zona fasciculata)--Produces cortisol Dense compact cells (zona reticularis)--Secrete androgens Adrenal medulla; lies below the zona reticularis--Produces catecholamines

catecholamines | adrenal medulla hormones

epinephrine norepinephrine dopamine

other sites of catcholamine production

Neurons of the sympathetic nervous system, CNS, chromaffin cells found in abdomen and neck

Methoxyhydroxyphenylglycol (MHPG) Vanillylmandelic acid (VMA) Homovanillic acid (HVA

metabolites of catecholamines

Initiate their respective biological actions via specific cell-membrane receptors: α-adrenergic and β-adrenergic receptors

norephinephrine: α-adrenergic receptors epinephrine: β-adrenergic receptors

functions of norepinephrine

**Vasoconstriction**, decreased insulin secretion, sweating, and stimulation of glycogenolysis in the liver and skeletal muscle

functions of epinephrine

**Vasodilation**, stimulation of insulin release, increased cardiac contraction rate, relaxation of smooth muscle in the intestinal tract, enhanced lipolysis, bronchodilation

may be significant in drug treatment of mental disorders (Parkinson’s disease and tardive dyskinesias)

dopamine

Catecholamine-producing tumors of the neurochromaffin cells

pheochromocytoma neuroblastomas

↑ VMA ↑ Metanephrines Normal Dopamine Normal HVA

pheochromocytoma

Catecholamine elevation may be induced by stress, upright posture, exercise, hypoglycemia, cold temps, and mental states of anxiety or anger

pheochromocytoma

Malignant neoplasm of neural crest origin Common in pediatric patients

neuroblastoma

↑ VMA ↑ Urinary Catecholamines ↑ Dopamine ↑ HVA

neuroblastoma

specimen handling for pheochromocytoma and neuroblastoma tests

24hour urine properly collected and preserved with **hydrochloric acid** to maintain acid pH, stored at **-80°C**

major glucocorticoid

cortisol

functions of cortisol

promotes gluconeogenesis, glycogenesis, lipolysis decreases glucose use suppresses immune system anti-inflammatory

CBG

coristol-binding globulin

explain RAAS

Renin (secreted by renal cells) acts on its substrate to produce angiotensin I, which is rapidly converted to angiotensin II in the lung by angiotensin-converting enzyme. Angiotensin II stimates aldosterone production. Aldosterone acts on the renal distal tubules to increase sodium retention and volume repletion, thus shutting off renin.

3 adrenal androgens, precursors to each other

Dehydroepiandrosterone (DHEA) Androstenedione Testosterone

stimulates hypothalamus to produce CRH

stress

no diurnal variation in cortisol

adrenal disorders such as adenomas and Cushing's

primary adrenal insufficiency

Addison's disease

Destructive events in the hypothalamus or pituitary gland that result in a decreased ability to secrete ACTH (secondary) or CRH (tertiary)

secondary or tertiary adrenal insufficiency

sx of Addison's

- bronzing of skin - postural HTN - hypoglycemia - changes in body hair - GI disturbances - weakness/muscle wasting - weight loss - hyponatremia - hyperkalemia

test used to dx Addison's

ACTH stimulation test (Cortrosyn test)

normal response to ACTH stimulation test

>20ug/dL of cortisol from the baseline

test used to dx secondary/tertiary adrenal insufficiency

Metyrapone stimulation

2 types of adrenal hyperfunction

- Cushing's syndrome: primary, low ACTH - Cushing's disease: secondary, high ACTH

70% cases caused by pituitary tumor

Cushing's disease (secondary)

Elevated levels of cortisol due to either medications or the presence of an adrenal tumor (adrenal adenoma)

Cushing's syndrome (primary)

17-OHCS test (urine)

Cushing's measures cortisol metabolites

Sensitive indicator of Cushing's because the increase is rapid as soon as plasma cortisol exceeds the binding capacity of CBG

urine free cortisol

sx of Cushing's

- buffalo hump - moon face - weight gain, thin extremities, edema - purple striae - male gynecomastia - facial acne - hyperglycemia - personality changes - amenorrhea, hirsutism - osteoporosis

used initially to establish true hypersecretion of cortisol

low dose dexamethasone suppression test

used to differentiate diagnosis of an ACTH-secreting pituitary adenoma

high-dose dexamethasone suppression test

adrenal aldosterone-producing adenoma

Conn's syndrome

hyperaldosteronism responsive to surgery

Conn's syndrome

adrenal hyperplasia, treated with drugs

idiopathic hyperaldosteronism

differentiate Conn's syndrome from IHA

Posture stimulation - Conn's/APA: Declining values on standing - IHA: Normal postural rise Most reliable: **Adrenal bilateral vein catheterization** and measuring serum aldosterone

Renal artery stenosis or renin-producing juxtaglomerular cell tumor of the kidney

causes secondary hyperaldosteronism

hallmark of secondary hyperaldosteronism

↑ urinary aldosterone in the presence of ↑ plasma renin activity

enlarged adrenal glands at birth decreased cortisol and aldosterone

congenital adrenal hyperplasia (CAH)

21-hydroxylase deficiency (most common) 11-hydroxylase deficiency (2nd most common)

congenital adrenal hyperplasia (CAH)

increased 17-OH progesterone, andostenedione, testosterone, estriol

congenital adrenal hyperplasia (CAH) causes virilization

sx of congenital adrenal hyperplasia

water wasting dehydration with hypotension hyponatremia hyperkalemia **virilization** failure to thrive

proteins that carry sex hormones

sex-hormone binding globulin (SHBG) cortisol-binding globulin (CBG) albumin

C18 sterol compounds

estrogens

Steroid hormone with 21 carbons

progesterone

Basal body temperature rises after... due to...

ovulation progesterone

any of the C19 sterols synthesized from cholesterol in the testes and adrenal glands

androgens

Primarily secreted by Leydig cell in male testes and female ovaries

testosterone

primary precursor of natural estrogens

DHEA (androgen)

test used to establish hypogonadism in males

hCG Stimulation Test

hCG should make testosterone ---

↑

Responsible for secretion of both gonadotropic hormones, LH and FSH

GnRH

binds to Leydig cell receptors to enhance conversion of cholesterol to testosterone

activates the seminiferous tubules for sperm production (in males)

FSH

Male has XXY chromosomes (47 karyotype), infertile, small testicles, sparse facial and body hair, reduced muscle mass, and enlarged breasts, low IQ

Klinefelter's syndrome

deficiency of GnRH during embryonic development in both males and females. Characterized by hypogonadism and lost sense of smell (anosmia).

Kallmann's syndrome

Defect in androgen receptor gene (testosterone level is normal/elevated) Female body build and development of breast tissue, intra-abdominal testes

Androgen Insensitivity Syndrome (AIS)

reduced efficiency of the conversion of testosterone to the more potent DHT. Males are born with ambiguous genitalia

5a-Reductase Deficiency (5-ARD)

↑ testosterone:DHT ratio

5a-Reductase Deficiency (5-ARD)

Increased estrogen:androgen ratio in males

gynecomastia

3 types of gynecomastia

1. **Transient**: 60-90% of all newborns from estrogen crossing the placenta (males and females) 2. **Puberty**: 50-70% of healthy boys. 3. **Adults**: 50-80 yrs old from testicular failure or ↑ body fat

enhances the effects of FSH on a maturing follicle

estradiol

A glycoprotein hormone that is secreted during pregnancy by the placenta

hCG

hcG first detected in maternal serum --- days following conception

6-9

Absence of menstruation by age 16, fail to develop secondary sex characteristics

primary amenorrhea

45 X karyotype (monosomy) Non-functioning ovaries By age 2, no eggs are left

Turner's syndrome

46 XX or XY karyotype (Swyer Syndrome)

pure gonadal dysgenesis

menstruation ceases for at least 6 months

secondary amenorrhea

infrequent menstruation that occurs < 9 times/year

oligomenorrhea

Genetically female, but phenotypic male characteristics Enzyme deficiency in pathway: 21-hydroxylase or 11β-hydroxylase which results in virilization

female pseudohermaphroditism

Characterized by infertility, hirsutism, obesity, irregular vaginal bleeding, and acanthosis nigricans (dark pigmentation of spiny layer of skin)

PCOS

Greater frequency of both hyperinsulinism & insulin resistance

PCOS

LH:FSH ration >2

PCOS

developmental anomaly of the placenta made up of trophoblastic tissue

Hydatidiform Mole

Leading cause of pregnancy-related, first-trimester death

ectopic pregnancy

main methods for measuring most hormones and metabolites

immunoassay techniques chromatography mass spectrometry

components of total testosterone measurement

- free (bioavailable) - albumin-bound (bioavailable) - SHBG-bound (unavailable)

Major circulating estrogen after menopause

estrone/E1

Most active of endogenous estrogens

estradiol/E2

Predominant urinary estrogen during pregnancy

estriol/E3

routinely used for identifying a fetus with Down Syndrome

unconjugated estriol/uE3

Any disruption in the biosynthetic pathway will lead to very low maternal serum -------------- levels.

unconjugated estriol

produced exclusively during pregnancy by the fetal liver

unconjugated estetrol/E4

No Estrogen ↑↑ LH & FSH

menopause

basic function of thyroid

Control basal metabolic rate and calorigenesis through increased oxygen consumption in tissue

secretory units of the thyroid gland that contain colloid

follicles

Amorphous material composed of thyroglobulin (Tg) and iodinated thyroalbumin

colloid

------ is ingested and converted to ------- by the thyroid, which is attached to tyrosine residues to give...

iodide iodine monoiodotyrosine (MIT) and diiodothyronine (DIT)

2 MIT

MIT + DIT

Once produced, T3 & T4 are stored as ------- in the colloid

thyroglobulin

Only about 20% of ------ is glandular, the rest is derived outside the thyroid gland through deiodination of -----, which takes place in the liver, kidney, and muscle

T3 T4

carriers of thyroid hormone

Thyroid-binding globulin (TBG) Thyroid-binding prealbumin (TBPA) Transthyretin (TTR) Serum albumin

major biologically active thyroid hormone

Causes an increase in number and size of follicular cells (hyperplasia) so they can trap more iodide to synthesize more thyroid hormones

TSH

bradycardia, hoarseness, cold sensitivity, dry skin, and muscle weakness

hypothyroidism

Diagnostic Test: Thyroid peroxidase (TPO) and antithyroglobulin antibodies

Hashimoto's thyroiditis

hypothyroidism with ↑ TSH and goiter

Hashimoto

Causes mental and physical restriction (cretinism) Must be detected early in newborns (first 3 months)

congenital hypothyroidism

Heat intolerance Tachycardia Weight loss Weakness/tremors Emotional lability/anxiety

hyperthyroidism

Thyroid Receptor Antibody (TRAb) Thyroid-Stimulating Antibody (TSI)

Graves disease

Graves disease triad

Exophthalmic eye (Eye bulging) Tremors Weight Loss

TT4

T4 bound (99.97%)

FT4 index purpose

measures the degree of unsaturation of TBG

T3 is helpful in confirming diagnosis of -----thyroidism, but not -----thyroidism

hyper- hypo- | does not reflect glandular secretion and often are normal

useful in patients who show equivocal signs and symptoms of thyroid dysfunction and when thyroid-function test results are not clearly diagnostic

Thyrotropin-Releasing Hormone Stimulation

Used clinically to differentiate nonthyroidal illness (NTI) from hypothyroidism

reverse T3

Directed against the thyroglobulin protein located within the thyroid colloid

Thyroglobulin Antibodies (TgAb)

Directed against a protein component of thyroid cell microsomes.

microsomal Ab

protection from radiation in nuclear disaster/atomic bomb

oral dose of potassium iodide before and/or after (<3-4 hours) exposure to saturate the thyroid-uptake system and prevent uptake of radioactive iodine

20) Endocrine Flashcards

(164 cards)