Thyroid Disease

Question 1

is this another word for hyperthyroidism or hypothyroidism: thyrotoxicosis

Answer 1

hyperthyroidism

Question 2

is this another word for hyperthyroidism or hypothyroidism: myxedema

Answer 2

hypothyroidism

Question 3

the thyroid gland synthesizes these two hormones that regulate the body’s metabolic rate

Answer 3

thyroxine (T4) (prohormone) and triiodothyronine (T3) (active hormone)

Question 4

explain the basic anatomy of the thyroid gland

Answer 4

• firm, reddish brown, smooth gland
• has two lateral lobes (right and left)
• has a pyramidal lobe that is centrally over the trachea

Question 5

the thyroid gland consists of many closely placed acini called _________ each surrounded by capillaries and stroma. its function is to trap dietary iodine and transport it into the colloid along with enzyme thyroidal peroxidase

Answer 5

follicles

Question 6

each follicle in the thyroid gland is roughly spherical, lined by a single layer of __________ epithelial cells

Answer 6

cuboidal

Question 7

the follice is filled with _________ which is a proteinaceous material composed mainly of thyroglobulin and stored thyroid hormones

Answer 7

colloid

Question 8

does this describe an active or inactive thyroid gland:
- follicles are large
- lining cells are flat
- colloid is abundant

Answer 8

inactive thyroid gland

Question 9

does this describe an active or inactive thyroid gland:
- follicles are small
- lining cells are cuboidal or columnar
- colloid is scanty
- edges are scalloped forming reabsorption lacunae

Answer 9

active thyroid gland

Question 10

scattered between follicles are _______ which secrete calcitonin (a hormone that inhibits bone resorption)

Answer 10

parafollicular cells (C cells)

Question 11

this glycoprotein is synthesized by the thyroid follicular cells, and contains many tyrosine residues

Answer 11

thyroglobulin

Question 12

true or false: the thyroid hormones remain attached to thyroglobulin until stimulated by TSH

Answer 12

true

Question 13

true or false: released thyroid hormones (T3 and T4) are water soluble and diffuse from the follicle into circulation

Answer 13

false - they are lipid soluble

Question 14

true or false: more of the thyroid hormone is in the form of T3 than T4

Answer 14

false - 90% of thyroid hormone is in the form of T4 whereas only 10% is in the form of T3 (T3 = active form)

Question 15

this form of iodine is absorbed and taken up by the thyroid

Answer 15

iodide

Question 16

iodide in the thyroid cell is oxidized to iodine which is catalyzed by what enzyme

Answer 16

thyroidal peroxidase

Question 17

during thyroid hormone synthesis, the iodine enters the colloid and is rapidly bound at the 3 position to tyrosine molecules attached to thyroglobulin forming _________

Answer 17

moniiodotyrosine (MIT)

Question 18

during thyroid hormone synthesis, MIT is iodinated at the 5 position forming __________

Answer 18

diiodotyrosine (DIT)

Question 19

during thyroid hormone synthesis, two DIT molecule then condense in an oxidative process catalyzed by thyroperoxidase to form _________

Answer 19

thyroxine (T4)

Question 20

both T3 and T4 are bound to plasma proteins such as

Answer 20

• albumin
• transthyretin
• thyroxine-binding globulin (TBG)

Question 21

does the free (unbound) or bound T4 and T3 inhibit pituitary TSH secretion

Answer 21

free/unbound

Question 22

which hormone (T3 or T4) has a longer half-life?

Answer 22

T4 has a long half-life (about 6-7 days)
T3 has a shorter half life (about 24 hours)

Question 23

Both T3 and T4 are metabolized in the liver, kidneys and many other tissues. they are conjugated into glucoronides in the liver and excreted into the ____

Answer 23

bile

Question 24

this thyroid hormone binds to its receptor and exerts its actions, mediated through alteration in gene transcription

Answer 24

T3

Question 25

this thyroid hormone is acted upon by cellular enzymes that cleave one of the iodine molecules to form the active form

Answer 25

T4

Question 26

thyroid hormone secretion is stimulated by pituitary __________

Answer 26

thyroid stimulating hormone (TSH)/thyrotropin

Question 27

Pituitary TSH secretion is stimulated by ________, a tripeptide secreted by the hypothalamus

Answer 27

thyrotropin releasing hormone (TRH)

Question 28

true or false: TSH secretion is inhibited by stress, dopamine and somatostatin

Answer 28

true

Question 29

true or false: free T4 and T3 act as a positive feedback loop to the anterior pituitary

Answer 29

false - negative feedback loop: more free T4 and T3 inhibits TSH release therefore less T4 and T3 released

Question 30

true or false: most thyroid diseases probably involves an autoimmune process

Answer 30

true

Question 31

transient hyperthyroidism is occasionally observed in patients with lymphocytic or granulomatous ___________ or ___________. in such cases, the hyperthyroidism is due to destruction of the thyroid with the release of stored hormone

Answer 31

subacute thyroiditis or Hasimoto disease

Question 32

what are some environmental factors that may cause hyperthyroidism

Answer 32

- infection - excessive iodide ingestion - amiodarone

Question 33

this disease is characterized by thyroid follicular cell hyperfunction with increased secretion of T4 and T3

Answer 33

grave's disease

Question 34

this disease is characterized by thyroid follicular cell destruction with release of T4 and T3

Answer 34

Hashimoto thyroiditis

Question 35

does this describe primary, secondary , tertiary or ectopic hyperthyroidism - thyroid gland affected - elevated levels of T3 and T4 - decreased levels of TRH and TSH

Answer 35

primary hyperthyroidism *note: if thyroid hormones are affected, thyroid gland is the culprit

Question 36

does this describe primary, secondary , tertiary or ectopic hyperthyroidism - hypophysis affected - elevated levels of TSH - T3 and T4 are also high, TRH is inhibited

Answer 36

secondary hyperthyroidism

Question 37

does this describe primary, secondary , tertiary or ectopic hyperthyroidism - the hypothalamus is affected thus TRH levels are affected

Answer 37

tertiary hyperthyroidism

Question 38

does this describe primary, secondary , tertiary or ectopic hyperthyroidism - a struma ovarii present (tumor in ovary that contains thyroid tissue)

Answer 38

ectopic hyperthyroidism

Question 39

this disease is the most common cause of hyperthyroidism among individuals in their third and fourth decades but can occur at any age. this disease is familial. a genetic contribution to the development of this disease is suggested by the finding of much higher concordance rates in monozygotic same-sex twin pairs than dizygotic. is associated with HLA-B8 and HLA-DR3 (in caucasians), HLA-Bw46 and HLA-B5 in (Asians) and HLA-B17 (in blacks), therefore other autoimmune disorders often accompany this disease. it is also more common in women

Answer 39

Graves disease

Question 40

the serum of more than 90% of patients with Grave's disease contains _____ antibody, directed against the TSH receptor site in the thyroid follicular epithelial membrane.

Answer 40

TSH-R [stim]

Question 41

what is the cause of the producing of TSH-R [stim] antibody?

Answer 41

unknown! could be molecular mimicry or suppressor T lymphocyte defect

Question 42

a defect in supressor T lymphocytes allows helper T lymphocytes to stimulate B lymphocytes to synthesize __________

Answer 42

thyroid antibodies (such as TSH-R[stim] Ab

Question 43

______ is the driving force for thyrotoxicosis

Answer 43

TSH-R [stim] Ab or TSI (same thing)

Question 44

inflammation of the orbital muscles (which is seen as bulging of the eyes) may be due to the sensitization of _________

Answer 44

cytotoxic T lymphocytes

Question 45

what are some clinical manifestations (signs and symptoms) of Hyperthyroidism

Answer 45

- changes in behaviour (e.g. insomnia, restlessness, palpitations, heat intolerance, sweating, etc. - increased appetite and dietary intake but paradoxical weight loss - changes in menstrual cycle

Question 46

what are some clinical manifestations (signs and symptoms) of Graves disease

Answer 46

- thyromegaly (increased size of thyroid gland) - exophthalmos (bulging of eye) - widening of the palpebral fissure resulting in exposed sclera (cannot close eyelids all the way) - vision changes (blindness, photophobia)

Question 47

untreated hyperthyroidism may decompensated into a state called __________, where excessive amounts go thyroid hormones are acutely released. patients have tachycardia, fever, agitation, N/V/D, psychosis, etc. could be caused by surgical emergency, infection, etc. should be treated aggressively as mortality rate is high

Answer 47

thyroid storm

Question 48

this is characterized by abnormally low serum T4 and T3 levels. the serum TSH level is elevated, as there is insufficient hormone available to inhibit the secretion of TSH.

Answer 48

hypothyroidism

Question 49

if TSH levels are elevated in hypothyroidism, this will cause thyroid cells to secrete large amounts of thyroglobulin which leads to a _______

Answer 49

goiter

Question 50

what are some causes of hypothyroidism

Answer 50

- most common: Hashimoto disease - lymphocytic thyroiditis - surgical removal of thyroid - iodine deficiency

Question 51

_____________ is caused by defects in TSH production which can result from - severe head trauma - cranial neoplasms - brain infections - cranial irradiation - neurosurgical procedures

Answer 51

secondary hypothyroidism (rare)

Question 52

what are some clinical manifestations (signs and symptoms) of hypothyroidism in infants

Answer 52

- routine screening is often mandatory - dull appearance - thick protuberant tongue and lips (makes it hard for baby to latch for feeding) - prolonged neonatal jaundice - poor muscle tone - bradycardia - umbilical hernia - hoarse cry

Question 53

what are some clinical manfiestaiotns (signs and symptoms) of hypothyroidism in children/adults

Answer 53

- decreased basal metabolic rate - weakness, lethargy, cold intolerance, decreased appetite - bradycardia - mild/moderate weight gain - elevated serum cholesterol and TGs - enlarged thyroid, dry skin, constipation - depression, difficulties with concentration/memory - menstrual irregularity

Question 54

edema due to accumulation of glycosaminoglycans in the interstitial spaces describes ___________-

Answer 54

hypothyroidism

Question 55

iodine deficiency is the most common cause of ________

Answer 55

goiter