Adv chemistry exam 2

Thyroid anatomy:

TSH vs fT4 graph

Female pituitary & sex steroids through course of menstrual period, and pregnancy

Primary adrenal Insufficiency:

hyperpigmentation

Cushing’s disease

striae

cushing's disease

supraclavicular fat deposits (buffalo hump)

cushing's disease

moon face (corticosteroid-induced lipodystrophy)

Grave’s disease

primary hyperthyroidism

goiter

hypothyroidism

thyroid eye disease

Aromatic steroid hormones

cholesterol, progesterone, estrone, androstenedione, testosterone, 17B-estradiol

Hypothalamic-Pituitary portal circulation

What pituitary hormone in excess causes goiter?

Prolonged elevation of TSH (thyroid stimulating hormone) levels due to iodine or hypothyroidism

What pituitary hormone deficiency causes adrenal atrophy and failure?

Deficiency in production of ACTH (adrenocorticotropic hormone)

Anterior pituitary hormones:

SH (Thyroid-stimulating hormone),
ACTH (adrenocorticotropic hormone),
HGH (Human Growth hormone),
LH (Luteinizing hormone),
FSH (stimulating follicle hormone),
PRL (prolactin)

Posterior pituitary hormones:

Oxytocin, antidiuretic hormone (arginine vasopressin)

Most common two pituitary adenomas

Somatotrophs Growth Hormone
Prolactin

Effect of hyperprolactinemia in males and females

Suppresses ovulation in both genders

- Males: infertility, lactation in male, breast development

- Females: infertility, menstrual irregularity

Negative feedback players on TRF/TSH & ACTH

TRF/TSH: Triiodothyronine (T3)
ACTH: Cortisol

Components of POMC

Secretion of ACTH and melanocyte stimulating hormones.
Y-MSH, ACTH (a-MSH and CLIP), and B-Lipotropin (Y-lipotropin (B-MSH), B-endorphin)
ACTH secreted as part of Proopiomelanocortin (POMC) precursor with melanocyte stimulating hormones

Function of thyroglobulin in physiology & thyroid cancer

Synthesized by follicular cells
Thyroglobulin (TG): useful as a post-treatment tumor marker of residual thyroid cancer
Useful tumor marker for post-treatment for differentiated thyroid cancer (recurrence)

ID Most potent thyroid hormone & most potent androgen

Thyroid hormone: T3 (Triiodothyronine)
Androgen: Dihydrotestosterone (DHT)

Match receptor type (Tyrosine Kinase)

T3 (Triiodothyronine)

Match receptor type: GCPR (G-protein coupled receptor)

trophic hormones – TSH (Thyroid stimulating hormone)

Match receptor type: Nuclear Steroid (glucocorticoid receptor

cortisol, thyroxine (T4), Triiodothyronine (T3)

What laboratory test(s) aid in identifying Congenital Hypothyroidism

Spot test for babies

What laboratory test(s) aid in identifying Chronic lymphocytic (Hashimoto’s) thyroiditis

autoantibody panels: serum anti-TPO, blocking TSIs or less sensitive anti-TG -- Anti TSH receptor antibody panel, Anti TPO, anti-thyroglobulin

What laboratory test(s) aid in identifying Graves’ disease

Autoantibody TSI, Antibodies screen or panel. Includes some of Hashimoto’s tests like Anti-TSH receptor antibody panel, Anti-TPO, anti-thyroglobulin test

What laboratory test(s) aid in identifying Subclinical hypothyroidism

perform a panel for T3, T4, TSH. Results Normal T3 and T4, high TSH

What laboratory test(s) aid in identifying Cushing’s Syndrome and Diseases

-Disease due to pituitary adenoma (Secondary cause of cortisol excess).
-Syndrome caused by cortisol excess from Stress, Cushing’s disease (cortisol excess from pituitary adenoma), Cushing’s syndrome (cortisol excess from any cause), Adrenal adenoma, Ectopic ACTH syndrome (paraneoplastic syndrome)

What laboratory test(s) aid in identifying
Primary Adrenal Insufficiency (Addison’s disease)

-Cosyntropin Stimulation test (Cosyntropin is hR ACTH fragment. Low dose stimulation (1ug) elicits cortisol peak of >18 ug/dL. (Used for suspected cortisol insufficiency)
-Dexamethasone suppression test (used for suspected cortisol excess)

What laboratory test(s) aid in identifying 21-hydroxylase (Congenital Adrenal Hyperplasia)

elevated 17-beta-hydroxyprogesterone levels, androgen, and cortisol

What laboratory test(s) aid in identifying Growth Hormone deficiency

provocative testing: stimulation tests using insulin-induced hypoglycemia or GHRH or suppression test. low IGF-1 (insulin-like growth factor-1 – surrogate marker – synthesized by liver).
-IGF-1 assay is preferred for GH deficiency or excess.
-GH secretion by pituitary adenoma: 75g oral glucose load suppression – adenoma not suppressed

Thyroid storm (Thyrotoxic crisis):

heart - acute exacerbation of thyrotoxicosis and presenting cardiac abnormalities.

Myxedema

Low T3, Low T4, high TSH. Severe hypothyroidism, Unresponsive hypometabolic state. Treatment: replacement hormone (levothyroxine).

Adrenal crisis (adenosine crisis)

hypoglycemia, hyperkalemia, mineralocorticoid deficiency, fluid imbalance.

Primary hyperthyroidism (Grave’s disease)

thyroid stimulating immunoglobulins (autoantibodies -TSI) activate TSH receptors causing over secretion of T4 and T3. Low TSH.

Secondary hyperthyroidism

pituitary function issue. Decreased TSH

Tertiary hyperthyroidism

hypothalamic issue. Decreased TSH.

Clinical findings of primary, secondary, and tertiary hyperthyroidism

anxiety, emotional lability, weak, tremor, palpitations, heat intolerance, increased perspiration, weight loss despite normal or increased appetite (thyroid storm/thyrotoxicosis

lab tests for primary, secondary, and tertiary hyperthyroidism

low TSH, overt hyperthyroidism

Primary hypothyroidism

increased serum TSH. Low Free T4

Secondary hypothyroidism

due to pituitary TSH deficiency. TSH normal or low. FT4 low.

Tertiary hypothyroidism

due to hypothalamic TRH deficiency

Clinical findings of primary, secondary, and tertiary hypothyroidism

fatigue, cold intolerance, weight gain, constipation, dry skin, myalgia, menstrual irregularities, bradycardia, hypertension, delayed relaxation phase of deep tendon reflexes (myxedema coma)

lab tests for primary, secondary, and tertiary hypothyroidism

elevated TSH, low Free T4. Majority of patients with Hashimoto’s (autoimmune thyroiditis) have elevated thyroid peroxidase (TPO) autoantibodies

Primary adrenal insufficiency (Addison’s disease)

deficiency in glucocorticoids or mineralocorticoids resulting in adrenocortical insufficiency resulting in destruction or dysfunction of Cortex. Produces renal wasting and potassium retention leading to severe dehydration. Hypotension, hyponatremia, hyperkalemia, and acidosis

Secondary adrenal insufficiency

deficiency in secretion of pituitary ACTH (adrenocorticotropic hormone). Caused by exogenous glucocorticoid therapy.

Tertiary adrenal insufficiency

deficiency in secretion of corticotropin-releasing hormone (CRH) from hypothalamus.

clinical findings in adrenal insufficiency

weak and fatigue, anorexia, weight loss, GI issues, nausea, vomiting, hyperpigmentation

lab tests in adrenal insufficiency

Cosyntropin stimulation test and rapid ACTH stimulation test. Hypoglycemia, hyperkalemia, hyponatremia, hypotension.

Cushing’s syndrome

from any cause including stress

Cushing’s disease

cortisol excess from pituitary adenoma, ACTH

clinical findings in cushing's

striae, supraclavicular and other fat deposits (buffalo hump, moon-face), delayed wound healing, impaired immune response.

lab tests for cushing's

Plasma ACTH, salivary, and 24 hr urinary cortisol, dexamethasone suppression test

21-Hydroxylase deficiency (CAH)

over secretion of adrenal androgens in females

clinical signs of 21-Hydroxylase deficiency (CAH)

females: excess adrenal androgens, virilization of fetus due to androgen excess, acne, hirsutism, clitoromegaly.
males: (Hercules)

tests for 21-Hydroxylase deficiency (CAH)

neonatal testing of elevated 17-beta-hydroxyprogesterone levels

Cosyntropin stimulation test

Cosyntropin is hR ACTH fragment with biological activity towards adrenal receptors. Low dose stimulation elicits cortisol peak >18 ug/dL in 1-2 hrs.

Dexamethasone suppression test

has potent negative feedback on ACTH release. High dose: 8 mg, most people with Cushing’s disease suppress, those with ectopic ACTH syndrome do not. Low dose: 1mg, AM cortisol >14, Cushing’s syndrome suspected.

Thyrogen stimulation test

synthetic TSH given to stimulate thyroid and unmask residual cancer

Provocative test

for growth hormone excess and deficiency – suppression and stimulation
GH secretion by pituitary adenoma: 75g oral glucose load suppression – adenoma not suppressed
GH deficiency: stimulation tests using insulin-induced hypoglycemia or GHRH

Iodine Deficiency

causes goiter (enlargement) – hypothyroidism – main one

Rate limiting step in steroid biosynthesis induced by ACTH

Conversion of cholesterol to Pregnenolone

Identify TPO inhibitors

Methimazole
Propylthiouracil (PTU)

Liver failure

low TBG, low SHBG, low CBG

Chronic illness

low SHBG, low CBG, low TBG

Pregnancy

high TBG, high SHBG, High CBG

Total hormone levels

low TBG, low CBG, low SHBG cause low total hormone
total T4 less informative than free T4

Tumor marker for medullary Thyroid Cancer

calcitonin

Salivary Cortisol:

used for accurate free cortisol levels in patients with abnormal serum-binding proteins. best in sensitivity and specificity for Cushing’s syndrome. Not normal nadir for people with Cushing’s

24-hr urinary Free cortisol tests

diagnosis of Cushing syndrome. Great for cortisol excess – poor for cortisol deficiency (adrenal insufficiency) – lacks sensitivity at low levels because low cortisol excretion can be found in normal levels of urine

Thyroid hormones

T3 and T4 bound by albumin, TBG and Transthyretin.
Free (unbound) TH are biologically active in combination with TH nuclear receptors and feedback loops. Responsible for oxidative metabolism at acceptable level for life – temperature, fever (metabolism high)

Cortisol

cortisol bound to albumin and CBG with free cortisol circulating. Plasma free cortisol is a biologically active cortisol regulated for ACTH

Diurnal rhythm of testosterone

highest levels early morning
lowest levels at midnight

Diurnal rhythm of Cortisol

peak early morning.

- 8 AM cortisol: 10-20 ug/mL.

- 4PM cortisol: 3-10 ug/mL.

- During sleep:

Diurnal rhythm of ACTH

peak early morning.

- 8AM ACTH: 10-50 pg/mL.

- 4PM ACTH:

Biochemical markers of Pheochromocytoma & Paragangliomas

Metanephrines

Normal doubling time of hCG in first trimester v. ectopic pregnancy

First trimester: 2-3 days (doubling)
Ectopic pregnancy: does not meet doubling time criterion – flat line

Pre-eclampsia

urinalysis screening

Neural tube closure defects

screening at 15-20 gestation. Alpha-fetoprotein measured first in maternal serum (MSAFP).

Fetal lung maturity

lecithin-sphingomyelin ratio (L/S ratio) (2:1) indicator. Phosphatidyl choline/glycerol (PC) another indicator (delayed in maternal DM). Thin layer chromatography detection

Differentiating urine from amniotic fluid

creatinine levels lower in amniotic fluid than urine. Fern test. pH (amniotic fluid 7.1-7.3, urine 4.5 – 6.0)

Cell free DNA screening (cf-DNA)

ratio of cell-free DNA from fetus and mom compared to determine trisomy
Also determines gender of the fetus and X/Y chromosomal abnormalities

Trisomy 21:

Down syndrome

Trisomy 18

Edwards syndrome

Trisomy 13

Patau syndrome

TLC (Thin Layer chromatography)

stationary phase: thin layer (coated plate)
hydrophobic or hydrophilic stationary phase

mobile: solvent that mixes up the liquid phase

GC (Gas chromatography)

stationary phase: capillary columns, coils can be packed with material (inside the column)
mobile phase: volatile gas (hydrogen)

affinity for either stage
a compound that has equal affinity for both stages

which of the following pathways is responsible for maintaining the change in water balance (increase in volume)

renin angiotensin aldosterone axis

method for neonatal screening tests

tandem mass spectrometry (MS/MS)

Identify major indications for monitoring therapeutic drugs

Compliance: medication has adverse effects
toxicity levels may be close to therapeutic ranges (Digoxin, lithium)

When should peak and trough drug levels be collected

peak: above minimum
15-30 minutes after intravenous injections or infusions
30-60 minutes after intramuscular injections
1 hours after drug taken orally
trough: below maximum
-immediately before next dose is given

Preferred methods for detecting aspirin, ethanol, and alcohols other than ethanol

Can be measured by enzymatic technique exploiting NADH production by ADH
Or identified and quantified by Gas chromatography

major metabolites of methanol

formic acid

major metabolites of ethylene glycol

glycolic acid
oxalic acid

major metabolites of isopropanol

acetone

major metabolites of ethanol

acetaldehyde
acetate

lethal ethanol concentration

50-100 mL
300-500 mg/dL

lateral flow immunoassay

-sample pad is the first stage of the absorption process
-conjugate pad stores conjugated labels and antibodies will get sample
-binding reagents on nitrocellulose membranes will bind to the target
-colored lines will form
-sample will pass through membrane into absorbent pad
-absorbent will absorb excess samples