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Biochem 3386 > Thyroid > Flashcards

Thyroid Flashcards

1
Q

Thyroid gland location

A

located in neck below larynx in front of trachea
right lobe larger than left
gland size is larger in areas of iodine deficiency
arranged around a central lumen

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2
Q

Colloid space

A

the central lumen that thyroid cells arrange around as follicles

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3
Q

Thyroid hormones are synthesized…

A

in follicular cells

stored on thyroglobulin in the colloid space

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4
Q

Thyroperoxidase (TPO)

A

oxidizes iodine coming into the thyroid gland so it can be added onto the tyrosyl moieties to create thyroid hormones

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5
Q

C-cells

A

synthesize hormone calcitonin

scattered within connective tissue holding together thyroid follicles

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6
Q

calcitonin

A

a hormone that helps prevents circulating free calcium level from getting too high

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7
Q

thyroxine (T4)

A

the major thyroid hormone
released bound to carrier proteins
stimulate cholesterol removal from the blood

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8
Q

tri-iodothyronine (T3)

A

10x more active than T4
mostly produced in peripheral tissues
released bound to carrier proteins
binds nuclear receptor proteins that initiate synthesis of proteins causing an increase in metabolic rate
stimulate cholesterol removal from the blood
generally follows the same pattern as T4

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9
Q

Negative feedback loop of thyroid hormone production

A

Thyroid hormones —| TRH —| TSH production

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10
Q

TSH function

A

stimulates iodine trapping and thyroid hormone synthesis and release of T3 and T4

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11
Q

sufficient dietary iodine leads to…

A

Decreased sensitivity of pituitary gland to TRH, limited secretion of TSH

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12
Q

insufficient dietary iodine leads to…

A

inadequate production of T4
pituitary increases its secretion of TSH
persistently high TSH levels lead to hypertropy of the thyrod gland

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13
Q

goitre

A

hypertrophy of the thyroid gland

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14
Q

Congenital hypothyroidism

A

lack of development of the thyroid gland OR enzyme defects in the pathway of thyroid hormone synthesis
can cause severe mental retardation

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15
Q

cretinism

A

severe mental retardation as a result of untreated congenital hypothyroidism

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16
Q

Acquired PRIMARY hypothyroidism

A

disease in the thyroid gland

Possible causes: removal of thyroid gland, autoimmune, excess intake of anti-thyroid drugs, iodine deficiency

17
Q

SECONDARY hypothyroidism

A

pathology in the pituitary gland (not enough secrestion of TSH)

18
Q

TERTIARY hypothyroidism

A

pathology in the hypothalamus (not secreting enough TRH)

19
Q

Clinical features of hypothyroidism

A 
low energy level, easily fatigued
weight gain
intolerance of cold temperature
dry skin and hair
hoarseness of voice
20
Q

Thyroid test profile: hypothyroidism

A

Low free T4 and T3, TSH can be high (primary) or low (secondary)

21
Q

Primary Hyperthyroidism

A

Graves disease (autoantibodies against TSH receptors in the thyroid gland)
Toxic multinodular goiter
Thyroiditis (inflammation of thyroid gland)

22
Q

Secondary hyperthyroidism

A

pituitary tumour that excretes TSH

elevated TSH and T3/4

23
Q

Clinical features of hyperthyroidism

A 
nervousness, hyperactivity
weight loss
heat intolerance
sweating
rapid heart rate
exophthalmous (bulging eyes)
24
Q

Test profile: hyperthyroidism

A

low TSH, high T3T4 (1)

high TSH, high T3/T4 (2)

25
Q

TSH as a clinical test

A

highly sensitive, analytically robust
most important for thyroid disease
primary screening test for all thyroid disease
log-linear relationship between T4 and TSH (2x T4 = 100x TSH) inverse

26
Q

TRH test:

A

rarely used

used to differentiate between secondary and tertiary hypothyroidism

27
Q

Thyroglobulin

A

follicular cell thyroid cancers produce high levels of thyroglobulin

28
Q

Calcitonin

A

a tumour marker for medullary (c-clel) carcinoma of the thyroid gland

29
Q

Anti-thyroid antibodies

A

ordered in the investigation of hypothyroidism

30
Q

Anti-TSH receptor antibodies

A

stimulatory (thyroid stimulating immunoglobins TSI or long acting thyroid stimulators LATS) can cause hyperthyroidism
or
inhibitory (thyroid binding inhibitory immunoglobulins TBII) can cause hypothyroidism

31
Q

parathyroid glands

A

four small glands located on or near the thyroid gland
secrete parathyroid hormone (PTH) which plays a role in calcium homeostasis
easily damaged
PTH interpreted with a serum calcium level

Biochem 3386 (14 decks)

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