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PHRM2101 > WEEK 3: Thyroid and Parathyroid > Flashcards

WEEK 3: Thyroid and Parathyroid Flashcards

1
Q

What are the two major communication systems in the human body?

A

the nervous system and the endocrine system.

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2
Q

What are the main
causes of endocrine diseases?

A

Aberrations in hormone secretion and/or action

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3
Q

T of F
every cell in the body is regulated in some way by the endocrine system.

A

T

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4
Q

Hormones can be classified according to their chemical structure. There are 3 main categories:

A

Peptide hormones
Amino acid derivitives
Lipid derivatives

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5
Q

Peptide hormones are comprised of…

A

amino acids.

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6
Q

What is the biggest hormone group?

A

Peptide hormones

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7
Q

Oxytocin, insulin, growth hormone, and follicle-stimulating hormone are all examples of … hormones.

A

peptide

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8
Q

human insulin is a polypeptide hormone comprised of … amino acid residues.

A

51

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9
Q

Thyroxine is formed from the condensation and modification of two … molecules.

A

Tyrosine

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10
Q

The amino acid … is the precursor for both adrenaline and the main thyroid hormone thyroxine.

A

tyrosine

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11
Q

Melatonin belongs to which hormone group?

A

amino acid derivatives

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12
Q

Amino acid derivates that are derived from either … or … are members of the amino acid derivative endocrine group.

A

the amino acid tryptophan or tyrosine.

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13
Q

Lipid derivatives that are derived from either … or … are members of the lipid derivative endocrine group.

A

arachidonic acid or cholesterol.

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14
Q

Eicosanoids (leukotrines, prostaglandins, thromboxanes, and prostacyclins) are members of which endocrine hormone group?

A

Lipid derivatives

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15
Q

Steroid hormones (oestrogens, progesterone, androgens, cortisol, aldosterone, calcitriol) are members of which endocrine hormone group?

A

Lipid derivatives

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16
Q

Thryoid hormones belong to which endocrine hormone group?

A

Amino acid derivatives

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17
Q

The catecholamines (dopamine, noradrenaline and adrenaline) belong to which endocrine hormone group?

A

Amino acid derivatives

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18
Q

T or F
Slight modifications of cholesterol’s structure produce similar hormones, with quite similar functions.

A

F
Slight modifications of the cholesterol’s structure produce different hormones, with quite distinct functions.

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19
Q

What is the definition of a “hormone”?

A

A signaling molecule that is secreted by an endocrine gland into circulation and acts on a distant target cell.

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20
Q

T or F
Hormones can be described as signalling molecules

A

T

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21
Q

T or F
In general, hormones are short-ranged messenger molecules.

A

F
In general, hormones are long-ranged messenger molecules.

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22
Q

T or F
Hormones often act on multiple tissues at the same time.

A

T

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23
Q

If hormones often act on multiple tissues at the same time, what gives hormones specificity of action?

A

whether cells express receptors or not for that hormone.

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24
Q

T or F
There is no such thing as short distance cell signalling

A

F
Though the cell signal here is not endocrine, but rather paracrine or autocrine.

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25
Q

Short cell signaling is performed by the … or … signaling systems.

A

paracrine or autocrine.

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26
Q

With short-distance cell signalling, the cell signalling molecules do not circulate in the blood to reach a distant target tissue. Rather, the signalling molecule is secreted out into … and acts on neighbouring cells, or even on the secreting cell itself.

A

interstitial fluid

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27
Q

T or F
Autocrine signalling is where signalling molecules secreted by the cells exert their effects on neighbouring cells in their immediate vicinity.

A

F
That is paracrine signalling

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28
Q

T of F
Autocrine signaling is where the signal secreted by a cell acts on its own receptors.

A

T
The “auto-“ prefix means “self”

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29
Q

Specificity of action with paracrine or autocrine signals is determined by …

A

whether or not neighboring cells express receptors, just like endocrine signaling.

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30
Q

Though endocrine signaling is dispersed via … . Paracine and autocrine signaling is dispersed through …

A

systemic circulation
simple diffusion

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31
Q

Endocrine diseases that cause too much hormone activity can be caused by…

A

Hypersecretion, reduced plasma protein binding, reduced clearance and excessive response at target tissue/s (rare)

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32
Q

Endocrine diseases that cause too little hormone activity can be caused by…

A

Hyposecretion, increased clearance and tissue resistance or insensitivity (common)

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33
Q

Neurohormones are hormones that originate from …, instead of endocrine glands.

A

neurons

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34
Q

In what way is the release of neurohormones like neurotransmitters?

A

They both release in response to electrical signals ie. action potentials.

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35
Q

T or F
The synapse of neurohormones is upon a network of blood capillaries and therefore neurohormones, like other ‘hormones’, circulate to have their effects.

A

T

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36
Q

The hypothalamus is part of what bodily system?

A

The central nervous system

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37
Q

What are two main parts of the pituitary gland?

A

the anterior and posterior pituitary.

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38
Q

T or F
The hypothalamus is located in the centre of the brain.

A

F
The hypothalamus is located at the base of the brain.

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39
Q

How is the hypothalamus connected to the pituitary gland beneath the brain?

A

by what is known as the infundibulum or pituitary stalk.

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40
Q

The hypothalamus is made up of … and … filled with cerebrospinal fluid

A

nuclei (concentrations of neuronal cell bodies)
nerve tracts (axons that surround the third ventricle)

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41
Q

What type of tissue is the hypothalamus?

A

neural

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42
Q

T or F
The hypothalamus is an endocrine gland.

A

T

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43
Q

Both the inputs and the outputs of the hypothalamus are … and …

A

Neural and humoral

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44
Q

The hypothalamus secretes …

A

neurohormones

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45
Q

What is a neurohormone?

A

a hormone that is produced or synthesised within neurons.

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46
Q

Name the 5 endocrine cell types

A

Somatotrophs, lactotrophs, thyrotrophs, Corticotrophs and Gonadotrophs

“Some tomatoes (somatotrophs) that lactate (lactotrophs) and have big thighs (thyrotrophin) court (corticotrophs) tomatoes with gonads (gonadotrophs)”

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47
Q

Name the two gonadotropins (hormones produced by gonadotrophs)

A

The Follicle stimulating Hormone (FSH) and Luteinising Hormone (LH)

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48
Q

What is the key role of the Follicle stimulating Hormone (FSH) and Luteinising Hormone (LH)?

A

Stimulate the gonads, including the production of sex steroid hormones.

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49
Q

What is the hormone produced by Corticotrophs?

A

Adrenocorticotrophic Hormone (ACTH)

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50
Q

What is the key role of Adrenocorticotrophic Hormone (ACTH)?

A

Stimulate the production of cortisol from the adrenal gland (adrenal cortex).

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51
Q

What is the key role of Thyroid Stimulating Hormone (TSH)?

A

Stimulate the production thyroid hormones from the thyroid gland.

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52
Q

What is the key role of Prolactin (PRL)?

A

Stimulate milk synthesis and secretion in lactation.

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53
Q

What is the key role of growth hormone in somatotroph cells?

A

to stimulate somatic cell growth.

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54
Q

What hormone is produced by Lactotrophs?

A

Prolactin (PRL)

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55
Q

T or F
Each of the anterior pituitary endocrine cells are functionally indiscreet (aka they are mostly dependent on each other)

A

F
Each of the anterior pituitary endocrine cells acts in large part independent of each other. That is, they are functionally discrete.

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56
Q

Name the 3 hypothalamic-pituitary axes

A

Hypothalamic-pituitary-thyroid (HPT) axis
Hypothalamic-pituitary-gonadal (HPG) axis
Hypothalamic-pituitary-adrenal (HPA) axis

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57
Q

the hypothalamic-pituitary-adrenal (HPA) axis is activated in response to…

A

stress

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58
Q

What is the endpoint of the hypothalamic-pituitary-adrenal (HPA) axis?

A

the hormone cortisol is released from the adrenal gland.

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59
Q

A stressor can be defined as…

A

any stimulus that causes activation of the HPA axis; and as a consequence an increase in circulating cortisol concentrations.

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60
Q

What does the hypothalamic-pituitary-adrenal axis control?

A

reactions to stress, regulates digestion, the immune system, mood and emotions, sexuality etc.

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61
Q

T or F
Thyroid glands and parathyroid glands are interchangeable terms

A

F
Thyroid glands should not be confused with the Parathyroid Glands which secrete entirely different hormones (with very different physiological functions), although they are co-located with the Thyroid Gland.

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62
Q

The two lobes of the thyroid gland are connected in the middle by a narrow strand called the …

A

isthmus

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63
Q

Thyroid follicles possess a central cavity that is filled with a sticky fluid called …

A

colloid

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64
Q

thyroid hormone production is dependent on which chemical element?

A

Iodine

65
Q

Within the spaces between thyroid follicles are the … cells (C cells) which secrete …

A

parafollicular
calcitonin

66
Q

T or F
A goitre can indicate both hyperthyroidism and hypothyroidism

A

T

67
Q

T or F
Tri-iodothyronine (T3) is less abundant than Tetra-iodothyronine (T4)

A

T

68
Q

Which protein is the substrate (precursor) for the synthesis of T3 and T4

A

Thyroglobulin (Tg)

69
Q

T or F
Thyroglobulin stores the inactive forms of thyroid hormone and iodine within the follicles.

A

T

70
Q

T3 can be produced in … by converting T4 to T3 via deiodination

A

peripheral tissues

71
Q

T or F
T4 undergoes peripheral synthesis

A

F
No peripheral synthesis. T4 (inactive) simply converted to T3 (active) hormone, as needed.

72
Q

T3 is how many times more potent than T4?

A

four times

73
Q

Select the correct onset of action for T3

a) Fast acting after secretion (within 2-3 hours)
b) Slow onset of action after secretion (~ 2-3 days)

A

a)

74
Q

Select the correct onset of action for T4

a) Fast acting after secretion (within 2-3 hours)
b) Slow onset of action after secretion (~ 2-3 days)

A

b)

75
Q

Select the correct duration of action for T3

a) Short duration of action (half-life ~ 1 day)
b) Long duration of action (half-life ~ 7 days)

A

a)

76
Q

Select the correct duration of action for T4

a) Short duration of action (half-life ~ 1 day)
b) Long duration of action (half-life ~ 7 days)

A

b)

77
Q

Select the correct protein binding for T3

a) Protein binding: 0.02% unbound (free fraction)

b) Protein binding: 0.2% unbound (free fraction)

A

b)

78
Q

Select the correct protein binding for T4

a) Protein binding: 0.02% unbound (free fraction)

b) Protein binding: 0.2% unbound (free fraction)

A

a)

79
Q

T3, rT3 is produced in the body via what two pathways?

A

T4 degradation/conversion in peripheral tissues (liver, kidney, muscle) or via direct secretion from the thyroid gland.

80
Q

T or F
Under normal physiologic conditions, the amounts of rT3 secreted are practically insignificant

A

T
(<1% of all thyroid hormones).

81
Q

T or F
reverse T3 (rT3) is an … of triiodothyronine (T3).

A

isomer

82
Q

Briefly describe Wilson’s Syndrome

A

Reverse T3 dominance (known as Wilson’s Syndrome) is used by some clinicians to describe a condition in which patients exhibit hypothyroid symptoms although circulating levels of T3 and T4 are within normal test limits – it is hypothesised that there is excess conversion of T4 into rT3 due to T4 malfunction.

83
Q

The thyroid releases calcitonin based on …

A

blood calcium levels

84
Q

T or F
Calcitonin is also known as thyrocalcitonin

A

T

85
Q

T or F
Calcitonin is also known as calcitriol

A

F
calcitriol is a Vitamin D derivative. Calcitonin is also known as thyrocalcitonin

86
Q

T or F
The hormone calcitonin regulates calcium levels in the blood by increasing them, opposing the actions of parathyroid hormone which decreases blood calcium levels.

A

F
The hormone calcitonin regulates calcium levels in the blood by decreasing it, opposing the actions of parathyroid hormone which increases blood calcium levels.

87
Q

What two processes cause calcitonin to be able to regulate blood calcium levels?

A

Calcitonin inhibits (blocks) the activity of osteoclasts (cells that break down bone). When osteoclasts break down bone, calcium is released from bone into the bloodstream. The temporary blocking of osteoclasts by calcitonin reduces the amount of calcium that enters the blood.

Calcitonin decreases the amount of calcium that the kidneys reabsorb and release back into the bloodstream, thus causing lower blood calcium levels.

88
Q

What is T4s main function?

A

T4’s main function is to facilitate the production of T3 when required.

89
Q

T or F
No receptors have been identified for T4.

A

T

90
Q

T or F
T3 acts on all tissues in the body

A

F
T3 acts on the majority of tissues within the body with a few exceptions (e.g., spleen).

91
Q

What effects can T3 have on tissues in the body?

A
  1. Increases the size and number of mitochondria within cells
  2. Increases Na-K pump activity
  3. Increases the turnover of various endogenous macromolecules
92
Q

How does T3 increase Na-K pump activity?

A

by increasing the production of the Na+/K+-ATPase

93
Q

How does T3 increase the turnover of various endogenous macromolecules?

A

by increasing their synthesis and degradation.

94
Q

What are the primary physiologic effect of T3 and T4?

A
  • Increases basal metabolic rate (increased heat generation and O2 consumption)
  • Increases metabolism (increased gluconeogenesis, glycolysis, glucose absorption, lipolysis and protein turnover)
  • Stimulates bone maturation and growth
  • Increases cardiac output (increased HR and contractility)
95
Q

Once inside the cell cytoplasm T4 can be deiodinated to T3 or rT3 depending on the …

A

enzyme expression.

96
Q

What type of receptor is a thyroid receptor?

A

A nuclear receptor

97
Q

Thyroid Receptors are nuclear receptors that function as …-dependent transcription factors

A

ligand-dependent

98
Q

Thyroid Hormones exert some profound physiological effects in the body. The main effects are:

A

Calorigenic or Thermogenic effects

99
Q

Thyroid Hormones (TH) stimulate … consumption in many cells of the body, resulting in increased metabolic rate and heat production as a consequence.

A

oxygen

100
Q

Thyroid Hormones are essential for normal … growth and … development.

A

somatic
neural

101
Q

Abnormal Thyroid Function Tests (TFTs) due to non-thyroidal illness is often referred to as either …

A

euthyroid sick syndrome or sick euthyroid syndrome

102
Q

How do thioamides (e.g., carbimazole, propylthiouracil - PTU) help with a dysfunctional thyroid gland?

A
  • Inhibit hormone synthesis by blocking peroxidase-catalyzed reactions (enzyme blocker)
  • Iodination of tyrosine residues of thyroglobulin (inhibit iodine binding to thyroglobulin), and coupling of DIT and MIT.
  • Inhibit peripheral conversion of T4 to T3 to some extent.
103
Q

T or F
Thioamides (e.g., carbimazole, propylthiouracil - PTU) are often used in older patients.

A

False
younger patients.

104
Q

T or F
Thioamides (e.g., carbimazole, propylthiouracil - PTU) are often used in patients with a mildly dysfunctional thyroid.

A

T

105
Q

T or F
Thioamides (e.g., carbimazole, propylthiouracil - PTU) inhibit release of pre-formed thyroid hormone.

A

F
thioamides do not inhibit release of pre-formed thyroid hormone à so onset of action is usually slow (3–4 weeks for full effect).

106
Q

What is the onset of action for Thioamides?

A

Usually slow, 3-4 weeks for full effect.

107
Q

T or F
Methimazole is preferred to PTU in pregnant and lactating patients.

A

F
PTU preferred in pregnancy because less likely to cross placenta and enter breast milk.

108
Q

Why is methimazole often the preferred thioamide?

A

Methimazole (carbimazole is prodrug of methimazole) preferred due to once daily dosing

109
Q

T or F
Both PTU and methimazole (carbimazole) can cause a major skin rash within the first 4-8 weeks of treatment.

A

T

110
Q

T or F
Despite its name, radioactive iodine is safe in pregnant and lactating patients

A

F

111
Q

T or F
Radioactive iodine is taken up in the same way as strong iodide salts and iodine supplements.

A

T

112
Q

T or F
An effective dose of Radioactive iodine (131I) can produce a permanent cure of thyrotoxicosis without surgery

A

T

113
Q

T or F
Despite its name, Radioactive iodine is interchangeable with strong iodide salts and iodine supplements.

A

F!

114
Q

How does radioactive iodine seek to cure hyperthyroidism?

A

By intentionally damaging the thyroid

115
Q

T or F
Radioactive iodine is most commonly used as a radiation treatment for patients with thyroid cancer.

A

T

116
Q

T or F
Anion Inhibitors are commonly used to treat thyroid disorders

A

F
they are rarely used clinically

117
Q

T or F
The effectiveness of anion inhibitors are predictable.

A

F
unpredictable

118
Q

What is the mechanism of action for anion inhibitors when treating thyroid disorders?

A

Block uptake of iodide by thyroid gland through competitive inhibition of iodide transporter

119
Q

T or F
Strong iodine salts and Iodine are not to be confused with OTC iodine products.

A

T

120
Q

Iodine supplements provide small amounts of iodine to support hormone synthesis; strong salts provides significant amounts of iodine to ultimately switch of hormone production via … mechanisms.

A

HPT axis feedback mechanisms.

121
Q

T or F
The effects of strong iodine salts and iodine are transient.

A

T

122
Q

Why are strong iodine salts and iodine often used in patients before a thyroidectomy?

A

strong iodine salts and iodine reduce the vascularity of the thyroid gland which thus minimises the risk of post-surgical bleeding

123
Q

When not being used pre-surgery, strong iodine salts, and iodine are used in patients with …

A

patients currently experiencing a thyroid storm

124
Q

T or F
Strong iodine salts and iodine are taken orally with water or juice to mask the metallic taste.

A

T

125
Q

Which chemical element is required to produce thyroid hormones triiodothyronine (T3) and thyroxine (T4)?

A

Iodine

126
Q

Thyroid replacement treatment with levothyroxine seems relatively straighforwards - we’re treatinga deficiency of hormones through direct replacements with synthetic equivalents. So, why might treatment fail?

A

a) non-adherence to treatment

b) impaired medication absorption (e.g., food, other drugs, malabsorption syndromes)

c) increased levothyroxine elimination (other types of drug interaction)

d) possible loss of tablet potency due to improper medication storage

127
Q

What glands are co-located with the thyroid gland?

A

parathyroid glands

128
Q

T or F
Parathyroid glands secrete similar hormones (with similar physiological functions) as the thyroid gland

A

F
The parathyroid glands - which secrete entirely different hormones (with very different physiological functions) - are co-located with the thyroid gland.

129
Q

T or F
A healthy parathyroid gland is the size of a grape

A

F
That is a diseased thyroid gland. A healthy thyroid gland is the size of a grain of rice.

130
Q

What colour are normal parathyroid glands?

A

the colour of spicy yellow mustard

131
Q

Which two parathyroid glands are deemed the “superior” parathyroid glands?

Upper left
Upper right
Lower left
Lower right

A

Upper left and right. The bottom left and right are deemed “inferior” parathyroid glands.

132
Q

T or F
The thyroid and parathyroid are related.

A

FALSE!
Although they are anatomical neighbours (hence the similar names) and both are part of the endocrine system, the thyroid and parathyroid glands are unrelated. They do not have the same functions.

133
Q

T or F
The parathyroid and thyroid are both part of the endocrine system.

A

T

133
Q

T or F
The parathyroid and thyroid are both part of the endocrine system.

A

T

134
Q

PTH is an essential regulator of … homeostasis

A

Calcium.
It plays a key role in the tight regulation of calcium levels in the blood.

135
Q

What is the most important element in our bodies?

A

Calcium.

136
Q

What is the only element with its own regulatory system?

A

Calcium via the parathyroid glands.

137
Q

Parathyroid glands produce …hormone.

A

parathyroid hormone

138
Q

Under physiological conditions calcium is absorbed via the … and excreted via the …

A

intestine
kidneys

139
Q

Where does the body store most of its calcium?

a) biomaterial
b) extracellular
c) intracellular

A

a) 99%

extracellular is 1%

intracellular is 0.01%

140
Q

Vitamin D3 is converted to … in the kidneys

A

calcitriol

141
Q

The calcium-sensing receptors (CaSRs) in the parathyroid gland which continuously monitor … calcium levels.

A

serum

142
Q

When a decrease in blood calcium level is detected, the CaSRs stimulate the glands to secrete …

A

parathyroid hormone (PTH).

143
Q

Once released from the parathyroid gland, PTH binds to the PTH-receptors on …, … and …

A

bone, kidneys and intestines.

144
Q

PTH stimulates the resorption of calcium from bone by increasing … number and activity.

A

osteoclast

145
Q

How do osteoclasts help raise blood calcium levels.

A

PTH stimulates the resorption of calcium from bone by increasing osteoclast number and activity. Resorption involves osteoclasts breaking down the tissue in bones to release minerals, resulting in a transfer of calcium from bone tissue to the blood.

146
Q

PTH promotes calcium (re)absorption/resorption (as opposed to calcium excretion) in the kidney by activating … in the …

A

adenylyl cyclase in the distal nephron.

147
Q

The … and … are the major sites of calcium absorption in the kidney.

A

proximal tubules (thick ascending limbs of Henle’s loop) and distal tubules

148
Q

PTH promotes calcium absorption in the gut by stimulating the formation of …-derived calcitriol

A

renally

149
Q

PTH is, in turn, down-regulated by serum calcium via …..

A

negative feedback.

PTH secretion is inhibited when calcium is at the required physiological level.

150
Q

T or F
Calcitriol is a hormone

A

F
it is a vitamin

151
Q

T or F
Calcitonin should not be confused with calcitriol

A

T
They are very different compounds.

152
Q

Calcitonin is a … hormone secreted by the ….. of the thyroid gland.

A

peptide
parafollicular C cells

153
Q

Calcitonin is secreted in response to a … in serum …

A

rise
calcium

154
Q

Calcitonin opposes the actions of …

A

PTH

155
Q

T or F
Calcitriol works in tandem with PTH to regulate calcium levels; PTH works quickly whereas calcitriol works slowly

A

T

156
Q

T or F
Parathyroid disorders always involve a calcium imbalance

A

T

157
Q

… is the precursor to osteoporosis.

A

Osteopenia

PHRM2101 (12 decks)

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