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MLSCI360 > HORMONES > Flashcards

HORMONES Flashcards

1
Q

What is the key to thyroid hormone synthesis ? Why ?

A
  • serum IODIDE is trapped in thyroid and incorporated into tyrosine
  • iodine transport into follicles is a rate-limiting step
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2
Q

How are thyroid hormones produced ?

A
  • thyrotropin releasing hormone (TRH) is secreted from hypothalamus in response to low T3 and T4
  • TRH stimulates production of TSH in the anterior pituitary
  • TSH binds to follicular cells of thyroid = secretion of triiodothyronine (T3), thyroxine (T4)*, and reverse T3
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3
Q

What is the major secretory product of the thyroid ?

A

thyroxine (T4)

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4
Q

How do T3 and T4 circulate in the blood ?

A

Bound to thyroid binding globulin (TBG)*, transthyretin, and albumin

*TBG has the greatest affinity for T4

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5
Q

How are T3 and T4 regulated ?

A
  • free T4 is deiodinated in the liver = active T3
  • T3 regulates rate of cellular oxidation (uptake of glucose) and protein metabolism
  • increased T3 and T4 inhibit anterior pituitary response to TRH
  • decreased thyroid hormones cause increase in TRH and TSH secretion
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6
Q

List 2 thyroid autoimmune diseases

A
  1. Graves’ disease; formation of autoantibodies specific to the TSH receptor = hyperthyroidism
  2. Hashimoto; cell-mediated autoimmunity causing thyroid dysfunction (goitre, thyroiditis, frequently hypothyroidism)
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7
Q

Endogenous Hypothyroidism

A
  • aka Hashimoto thyroiditis
  • autoimmune thyroid disease
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8
Q

Exogenous hypothyroidism

A
  • Graves’ disease
  • associated with iodine imbalance and various medications
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9
Q

Secondary hypothyroidism

A

Due to damage/disease of hypothalamus/ pituitary gland

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10
Q

Endogenous hyperthyroidism

A
  • aka Graves’ disease
  • associated with thyroid tumors and disorders of hypothalamus/ pituitary gland
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11
Q

Exogenous hyperthyroidism

A
  • associated with viral and bacterial thyroiditis
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12
Q

Describe Non-thyroidal Illness (NTI)

A
  • low total and free T3; elevated REVERSE T3; normal to low TSH
  • seen in starvation, sepsis, surgery, myocardial infarction, diabetes…
  • lack of conversion of T4 to T3 at the tissues
  • suppresses TRH release, reduced T3 and T4 turnover, reduction of T3 at liver, tissue-specific down-regulation of receptors, transporters, and enzymes
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13
Q

What is the most sensitive and specific test for the investigation and management of primary thyroid dysfunction ?

A

TSH testing; in comparison with T4, TSH is not markedly affected by NTI or drugs

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14
Q

Which subunit of hCG is specific to the placenta ?

A

β* = specific to placenta

α = TSH, LH, and FSH

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15
Q

What does hCG do ?

A

hCG acts on corpus luteum to produce progesterone until placenta can produce enough progesterone to maintain pregnancy

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16
Q

Clinical application of qualitative hCG serum

A

Used to diagnose pregnancy

17
Q

Clinical Applications of Quantitative serum/ plasma hCG

A
  • date pregnancy
  • detect multiple pregnancies (2X in twins)
  • assist in detection of ectopic pregnancies
18
Q

Clinical Applications of increased intact hCG and free β subunit

A
  • Trophoblastic disease
  • Germ cell tumours
  • Other cancers (biliary, pancreatic)
19
Q

What is used to monitor treatment and progression of trophoblastic disease ?

A

Serial measurement of hCG

20
Q

What is First Trimester Screening used for ?

A
  • determine risk of having a fetus with serious birth defects
    Ie. Neural tube defect or Down’s Syndrome
  • performed between 10 to 13 weeks’ gestation
  1. hCG in blood = increased
  2. pregnancy associated plasma a protein A = increased
  3. Nuchal Translucency Test = increased nuchal space
21
Q

What results in the First Trimester Screening would indicate a Trisomy ?

A
  1. hCG in blood = increased
  2. pregnancy associated plasma a protein A = increased
  3. Nuchal Translucency Test = increased nuchal space
22
Q

What is the Second Trimester Screen ?

A
  • aka Multiples of the Median/ Quad Screen
  • prenatal testing to estimate risk of open spina bifida, anencephaly, trisomy 21 and trisomy 18
  1. Alpha-fetoprotein (AFP) = increased
  2. Human chorionic gonadotropin (hCG) = increased
  3. Unconjugated estriol 3 = increased
  4. Dimeric Inhibin A = increased
23
Q

What results in the Second Trimester Screening would indicate fetal abnormality ?

A
  1. Alpha-fetoprotein (AFP) = increased
  2. Human chorionic gonadotropin (hCG) = increased
  3. Unconjugated estriol 3 = increased
  4. Dimeric Inhibin A = increased
24
Q

What is MoM ?

A
  • multiple of the median
  • statistical value measures how different patient results is from the median of a similar population
  • patients with a greater MoM result than the cut-off value will have additional testing
25
Q

T or F: The cut-off MoM value does NOT have a 100% positive or negative predictive value

A

TRUE; The cut-off MoM value does NOT have a 100% positive or negative predictive value

MLSCI360 (22 decks)

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