Chemistry - Osler: Thyroid And Adrenal

Front 1

What is the predominant thyroid product?

Back 1

T4 (90-95%)

Front 2

What is the rate limiting step when TSH is high?

Back 2

iodine rate

Front 3

What is the active thyroid hormone?

Back 3

T3

Front 4

How is t3 transported peripherally?

Back 4

99.7% protein bound, inactive, unregulated

Front 5

Where is most T3 produced?

Back 5

Liver and kidney by action of monodeiodinases

Front 6

What is the clinical significance of normal total T4 and T3 levels?

Back 6

It effectively rules out thyroid disease (central 75%)

Front 7

What is euthyroid sickness?

Back 7

Conversion of T4 to T3 is inhibited. This causes normal total and free T4, normal T3RU, decreased T3 and normal TSH.

Front 8

What is the most important test for evaluating for thyroid disease?

Back 8

TSH

Front 9

How does T3 resin uptake testing work?

Back 9

Labeled T3 is bound to the patient's serum. The excess labeled T3 is bound to a resin, and that is measured and is inversely proportional to the amount of TBG binding sites available in the patients serum.

Front 10

What is the normal amount of available TBG binding sites?

Back 10

40% free

Front 11

What is the status of T4 and T3 resin uptake in hyperthyroid?

Back 11

Both increased. Hyperthyroid means less available binding sites on TBG, means more label taken up in the resin

Front 12

What is the status of T4 and T3 resin uptake in hypothyroid?

Back 12

Decreased T4 and resin uptake

Front 13

What is the status of T4 and T3 resin uptake in patients with a high level of TBG?

Back 13

Increase T4 and decrease resin uptake

Front 14

What is the status of T4 and T3 resin uptake in patients with a low level of TBG?

Back 14

Decreased T4 and increased resin uptake

Front 15

What antibody is specific for graves disease

Back 15

thyroid stimulating immunoglobulin

Front 16

When is thyroglobulin useful?

Back 16

As a thyroid tumor marker

Front 17

What is the first finding in hyperthyroidism?

Back 17

Suppressed TSH

Front 18

What gets elevated first in graves?

Back 18

T3 before t4, free before total, normal t3 suggests another cause

Front 19

What is the first finding in hypothyroidism?

Back 19

Increased TSH, usually > 50 mU/Lfollowed by
low free, total, t3RU

Front 20

How does pregnancy affect thyroid values?
TBG, T3, total t4, free t4, resin uptake?

Back 20

High total t4 and T3, low t3 resin uptake, normal TS, normal free t4

Front 21

How does cirrhosis/nephrotic syndrome affect thyroid values?

Back 21

Low total t4, high T3RU, normal TSH, normal free t4

Front 22

How does acute illness change thyroid values?

Back 22

Decreased t3 (low peripheral conversion), normal total/free t4, tsh

Front 23

Explain the cyclic production of glucocorticoids

Back 23

Highest on waking, lowest in early sleep

Front 24

How does stress affect cortisol?

Back 24

Stimulates IL-6 and serotonin, minimizes cyclic production, Increased Cortisol and ACTH

Front 25

What stimulates cortisol production?

Back 25

ACTH

Front 26

True or false, cortisol is mostly protein bound

Back 26

True

Front 27

How is urine free cortisol affected by hypercortisolism?

Back 27

Increases exponentially over serum concentration
plasma 2x, urine 50x normal

Front 28

What urine metabolite measures androgens (not testosterone)

Back 28

17 ketosteroids. By colormetric assay

Front 29

What urine metabolite measures cortisol, precursor, and metabolites

Back 29

17-hydroxysteroids. By colormetric assay

Front 30

What is cushing disease?

Back 30

Pituitary ACTH production

Front 31

ACTH undetectable or low, cortisol, is not suppressed by high or low doses. Diagnosis?

Back 31

Primary Hypercortisolism

Front 32

Explain pituitary stimulation

Back 32

Metyrypone blocks 11 hydroxylase, normal response is for cortisol to fall, but ACTH and 11 deoxycortisol to rise by at least 7

A more sensitive test (but more dangerous!) is for insulin hypoglycemia to stimulate ACTH and cortisol levels to >18-20

Front 33

What is another name for T4?

Back 33

free thyroxine

Front 34

What two antibodies do you find elevated in Hashimoto's Disease?

Back 34

anti-microsomal or anti-thyroid peroxidase (anti-TPO)

Front 35

What 3 antibodies do you find elevated in Graves? Which one is specific for Graves?

Back 35

1) anti-microsomal

2) anti-thyroid peroxidase

3) anti- thyroid stimulating immunoglobulins (TSI) - this is specific for Graves

Front 36

what is the single best test for detection of hyperthyroidism?

Back 36

TSH

Front 37

what is the single best test for detection of hypothyroidism?

Back 37

TSH

Front 38

What can increase the TBG?

Back 38

active liver injury, pregnancy and many drugs including estrogens, estrogen dominent OCP, phenothiazines and opiates

Front 39

what can decrease the TBG?

Back 39

protein losing states, cirrhosis, congenital deficiency

Front 40

What stimulates the production of cortisol?

Back 40

stress, inflammation (IL-6), darkness, serotonin, hypoglycemia

Front 41

what inhibits the production of cortisol?

Back 41

light, glucose, synthetic steroids such as dexamethasone

Front 42

what are 2 false positive for the dex suppression test?

Back 42

obesity (most of the drug goes into the fat), increased liver metabolism (by other drugs like alcohol and pheytoin) and renal failure (may not absorb dex)

Front 43

for adrenal stimulation tests, what do you give?

Back 43

cortosyn or cosyntropin. A serum cortisol increase to >18-20 confirms intact adrenal

Front 44

describe the dex suppression test

Back 44

1) overnight, do screen. Give 1mg and expect the serum cortisol to be <3 in a normal person

2) Give low dose 0.5mg. If the URINE cortisol <10, then it is not cushing. If the URINE cortisol >10, then maybe cushing

3) give high dose. This is to find out if the patient has a pituitary problem. If there is a FALL in the URINE free cortisol <20% or the SERUM free cortisol <50%, then the patient has pituitary problem (cushing DISEASE)

4) If the patient didn't have a fall in cortisol, then measure ACTH. If there is high ACTH, it is ectopic cortisol production. If there is low ACTH, then there is an adrenal tumor.

Front 45

what is addison's disease?

Back 45

primary adrenal failure.

Front 46

What test do we do to distinguish primary from secondary adrenal insufficiency?

Back 46

measure cortisol before and after stimulation with cortrosyn

If cortisol is low, high ACTH confirms primary adrenal insufficiency, while low ACTH is seen in secondary (or tertiary) adrenal insufficiency

Front 47

Congenital adrenal hyerplasia:

which have HTN? virilization?

Back 47

deficiencies that begin with the number 1 have HTN (e.g. 11 hydroxylase and 17 hydroxylase)

Deficiencies that end with number 1 have virilization (e.g. 21 and 11 hydroxylase)

Front 48

in 21-hydroxylase deficiency, what s the compound that accumulates?

Back 48

17-OH Progesterone

Front 49

When are renin and aldosterone at their lowest levels? highest?

Back 49

lowest in morning and in supine position

highest in afternoon and in upright position

Front 50

how must renin samples be handled?

Back 50

room temperature to prevent false increases

hypokalemia inhibits aldosterone production and should be corrected prior to testing aldosterone or renin levels

Front 51

What stimulates renin production?

Back 51

decreased blood flow, decreased urine sodium, diuretics, allowing specimen to sit at 4C (artifact), hyperkalemia

Front 52

what inhibits renin production?

Back 52

NSAIDS, beta blockers, ACE inhibitors, hypokalemia, heparin, atrial natriuretic hormone, adrenal disease

Front 53

what are the renin and aldosterone levels for primary and secondary hyperaldosteronism?

Back 53

primary: decreased renin and increased aldosterone

secondary: increased renin and increased aldosterone

Front 54

what can increase catecholamines?

Back 54

stress and caffeine.

prolonged excess of catecholamines adernal medulla tumor such as neuroblastoma or pheochromocytoma

Front 55

what do we measure for neuroblastoma?

Back 55

HVA and VMA