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From Flashcardlet > Clinical Lab Med 7 - Encocrinology > Flashcards

Clinical Lab Med 7 - Encocrinology Flashcards

1
Q

What is the chain of common to the thyroid gland, organs only?

A

Hypothalamus
Anterior pituitary
Thyroid

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2
Q

What hormone does the hypothalamus secrete to stimulate the anterior pituitary?

A

Thyrotropin releasing hormone (TRH)

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3
Q

What hormone does the anterior pituitary secrete to stimulate the thyroid?

A

Thyroid stimulating hormone (TSH)

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4
Q

What hormones does the thyroid secrete?

A

T3 and T4

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5
Q

What is the feedback system from the thyroid to the anterior pituitary?

A

When T3 and T4 levels are low, the anterior pituitary recognizes this and is stimulated to secrete more TSH

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6
Q

What happens to the anterior pituitary gland when T3 and T4 levels are high?

A

Feedback is sent back to the anterior pituitary gland to suppress the secretion of TSH

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7
Q

Does feedback go to the hypothalamus dependent on levels of T3 and T4?

A

Yes, feedback goes to the anterior pituitary and the hypothalamus, but the feedback to the hypothalamus is immeasurable

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8
Q

What hormone don’t we measure when looking at thyroid function?

A

Don’t measure TRH from the hypothalamus

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9
Q

What does TRH stand for?

A

Thyrotropin releasing hormone

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10
Q

What is the name of T3?

A

Triiodothyronine

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11
Q

What is the name of T4?

A

Thyroxine

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12
Q

What is the gold standard for measurement of pituitary function?

A

TSH

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13
Q

What is second to the gold standard for measurement of pituitary function?

A

Free T4

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14
Q

Which hormone is the most sensitive measurement of thyroid function?

A

TSH

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15
Q

What is the difference between T4 and free T4?

A

Free T4 is the remainder of the T4 that is not bound to a protein, and is therefore active

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16
Q

Why are the thyroid hormones unique compared to other hormones in the body?

A

Contain iodine

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17
Q

Where is iodine absorbed and taken up in the thyroid?

A

Absorbed in the intestine and taken up by thyroid’s follicle cells

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18
Q

What is the iodine concentration in the thymus compared to the concentration in the plasma?

A

Iodine concentration is 50 times greater than that of the plasma

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19
Q

What might we suspect in patients from countries that have iodine deficiency?

A

Thyroid deficiency

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20
Q

What substances combine to form T3 and T4?

A

Iodine is used in combination with other amino acids

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21
Q

What proteins are T3 and T4 bound to in the blood?

A

Alpha globulins

Albumin

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22
Q

What is the principle protein involved in T3 and T4 binding?

A

Thyroxine binding globulin (TBG)

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23
Q

What thyroid hormones are responsible for stimulating target tissues?

A

Small quantity of unbound thyroid hormones that circulate in the plasma

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24
Q

What cells do the thyroid hormones target?

A

Virtually all cells

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25
Q

What is the major effect of thyroid hormones?

A

Metabolic, promoting utilization of carbohydrates, protein, and lipids

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26
Q

Why does it mean in terms of presenting symptoms if thyroid hormones target virtually all cells?

A

Vast variety of symptoms

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27
Q

What are the primary effects of thyroid hormones?

A
  • Aerobic energy metabolism
  • Glucose metabolism
  • Protein metabolism
  • Lipid metabolism
  • Ion transport
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28
Q

What are the secondary effects of thyroid hormones?

A
  • Growth/development
  • Cardiac output
  • Ventilation
  • CNS activity
  • Thermoregulation
  • Muscle function
  • GI activity
  • Reproductive functions
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29
Q

What is a general characteristic of hyperthyroidism?

A

Fast symptoms - tachycardia, hypertension

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30
Q

What is a general characteristic of hypothyroidism?

A

Slow symptoms - bradycardia, hypotension

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31
Q

What are two causes of thyroid disease?

A
  • Malfunction of the gland itself

- Defect in the anterior pituitary-hypothalamus control system

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32
Q

What is the main result of hypothyroidism?

A

Thyroid hormone secretion is inadequate to maintain normal levels of target tissue stimulation

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33
Q

What are the two most common causes of hypo secretion?

A

Surgical resection or radiation therapy for hypersecretion

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34
Q

Why are we okay with over treating hyperthyroidism and then resulting with hypothyroidism?

A

Because hyper is much more dangerous

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35
Q

What is cretinism?

A

Disorder seen in newborns where normal growth and tissue differentiation are impaired

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36
Q

What are some other causes of thyroid hypo function besides over treatment of hyperthyroidism?

A
  • Penetrating wounds to neck
  • Bacterial/viral infections
  • Iodine deficiency
  • Insufficient stimulus by hypothalamus/pituitary
  • Therapeutic drugs with thyroid blocking effects
  • Pregnancy and puberty
  • Hashimoto’s’ thyroiditis
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37
Q

Why do penetrating wounds to the neck cause thyroid hypo function?

A

Produce inflammation and interrupts cell function

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38
Q

How do bacterial or viral infections cause thyroid hypo function?

A

Infections of the mouth or throat can spread to the thyroid, causing cell damage

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39
Q

How does pregnancy or puberty cause thyroid hypo function?

A

Increased demand on thyroid hormones due to changes in the body and the gland can’t keep up with the demand

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40
Q

What is Hashimoto’s thyroiditis?

A

Autoimmune disease where body is making antibodies against the thyroid

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41
Q

How does Hashimoto’s cause thyroid hypo function?

A

Inflammation from antibodies against the thyroid result in fibrosis, causing a loss of function of the cells

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42
Q

What are some symptoms of hypothyroidism?

A
  • Weakness
  • Fatigue (exercise intolerance)
  • Cold intolerance
  • Weight gain
  • Constipation
  • Bradycardia
  • Memory loss
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43
Q

What are some causes of thyroid hyper function?

A
  • Excess thyroid hormones
  • Thyroid injury (rare)
  • Thyroid tumors
  • Toxic nodular goiter
  • Grave’s disease
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44
Q

What is the most common cause of hyper function of the thyroid?

A

Grave’s disease

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45
Q

Why does goiter cause hyper function of the thyroid?

A

Increased size and number of cells, increased function of the structure

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46
Q

What do antibodies of Grave’s disease act like?

A

They act as if they were TSH, stimulating the TSH receptors to stimulate thyroid secretion

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47
Q

How large does the thyroid gland get in Grave’s disease?

A

2-3 times normal size

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48
Q

What kind of disease is Grave’s disease?

A

Autoimmune

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49
Q

What are the antibodies in Grave’s disease formed against?

A

Against TSH receptors, not thyroid cells themselves

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50
Q

What is the main physical sign of Grave’s disease?

A

Exopthalmos - bulging eyes

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51
Q

Is exopthalmos reversible in Grave’s disease?

A

Yes, reversible with treatment

52
Q

What are some symptoms of hyperthyroidism?

A
  • Muscle wasting
  • Increased activity
  • Heat intolerance
  • Weight loss
  • Insomnia
  • Diarrhea, nausea, and vomiting
  • Tachycardia
  • Tremor
53
Q

Why does muscle wasting and weight loss present with hyperthyroidism?

A

Increased metabolic activity burns more calories and fat

54
Q

Why does hyperthyroidism cause vomiting and diarrhea?

A

Increased peristalsis

55
Q

Which hormone in thyroid disease is rarely measured?

A

T3 - not as specific as T4 or TSH

56
Q

What lab test do we use to measure autoimmune thyroid disease?

A

Antithyroid antibody levels

57
Q

What does TSH and T3/4 levels look like with hypothyroidism?

A

Increased TSH

Decreased T3/4

58
Q

What are the antibodies that are associated with Hashimoto’s thyroiditis?

A

Anti-TPO (anti-thyroid peroxidase antibodies)

59
Q

What does TSH and T3/4 levels look like with hyperthyroidism?

A

Decreased TSH

Increased T3/4

60
Q

What are the antibodies that are associated with Grave’s disease?

A

Anti-TSH receptor antibodies

61
Q

Why is TSH increased with hypothyroidism?

A

Thyroid disease is based on function of thyroid and levels of thyroid hormones (T3/4)
If T3/4 levels are low, the anterior pituitary gland is signaled to release more TSH, trying to increase the production of thyroid hormones

62
Q

What would we do if we saw a mixed lab picture, of Increased TSH and T3/4?

A

We would search with imaging, maybe there is a tumor on the anterior pituitary that causes constant release of TSH and therefore constant production of T3/4

63
Q

What is the treatment for hypothyroidism?

A

Supplement with thyroid hormone replacement

64
Q

How long does it take for supplement of thyroid hormone to stabilize TSH levels?

A

6 weeks

65
Q

How often should TSH be measured with thyroid hormone replacement?

A

Every 6-12 months

66
Q

What are two different kinds of thyroid hormone replacement options?

A

Natural - animal TSH

Synthetic TSH

67
Q

What do the hormones that are secreted by the adrenal glands do for the body?

A

Enable patients to cope with changing environments

68
Q

Where are the adrenal glands located?

A

Pair of small glands that rest o the superior pole of each kidney

69
Q

What is the collective term for the hormones produced by the adrenal glands?

A

Corticosteroids

70
Q

What do mineral corticoids affect?

A

Sodium and potassium

71
Q

What do glucocorticoids affect?

A

Carbohydrate metabolism

72
Q

What is another name for glucocorticoids?

A

Cortisol

73
Q

What do gonadocorticoids affect?

A

They are sex hormone precursors

74
Q

What hormone regulates cortisol and gonadocorticoid synthesis?

A

ACTH - adrenocorticotropic hormone

75
Q

What gland secretes ACTH?

A

Anterior pituitary

76
Q

What does ACTH stand for?

A

Adrenocorticotropic hormone

77
Q

What hormone regulates the secretion of ACTH?

A

CRH - corticotropin-releasing hormone

78
Q

What gland secretes CRH?

A

Hypothalamus

79
Q

What does CRH stand for?

A

Corticotropin-releasing hormone

80
Q

What is the chain of command for regulation of corticosteroids?

A

Hypothalamus - CRH
Anterior pituitary - ACTH
Adrenal glands - secrete glucocorticoid and gonadocorticoid

81
Q

What hormone regulates the mineral corticoid pathway?

A

Angiotensin II

82
Q

What is Cushing’s syndrome and disease caused by?

A

Excess glucocorticoids

Adrenal tumors

83
Q

Why does the body have excess glucocorticoids?

A

Prolonged ACTH stimulation

Prolonged glucocorticoid therapy for other conditions

84
Q

What is Cushing’s disease (as opposed to syndrome)?

A

Disease is when the disorder is caused by a pituitary lesion

85
Q

What is Cushing’s syndrome (as opposed to disease)?

A

Syndrome is a way to describe any condition that produces an elevation in glucocorticoid levels (problem with the adrenal gland itself)

86
Q

What are the physical presentations of Cushing’s disease?

A
  • Round moon face, puffy cheeks
  • Muscle weakness
  • Hypertension
  • Fat deposition in abdomen and base of neck
  • Thin arms and legs
87
Q

What happens in Cushing’s disease due to the lesion on a pituitary gland?

A

Excess ACTH is produced from a pituitary tumor

88
Q

What are some causes of secondary Cushing syndrome?

A
  • Hypothalamus tumor

- Nonendocrine tumor like bronchogenic carcinoma

89
Q

What happens to ACTH levels in secondary Cushing syndrome?

A

Tumors not on the anterior pituitary gland secrete ACTH

90
Q

Why are there increased levels of glucocorticoid in Cushing’s disease?

A

Because the lesion on the anterior pituitary produces excess ACTH

91
Q

What is Conn’s syndrome?

A

Primary hyperaldosteronism - hyper secretion of the aldosterone secreting cells of the adrenal cortex

92
Q

What is Conn’s syndrome usually a result of?

A

Cortical adenoma

93
Q

What is a systemic symptom of Conn’s syndrome?

A

Systemic hypertension due to sodium and water retention by the kidney

94
Q

What is secondary hyperaldosteronism caused by in general?

A

Increased stimulation of the RAA system from somewhere else in the body (not from the adrenal cortex)

95
Q

What are some specific examples of what secondary hyperaldosteronism caused by?

A
  • CHF
  • Pregnancy
  • Decreased renal perfusion
  • Hypoalbuminemia
96
Q

What are some ways corticosteroid deficiency is caused?

A
  • Destruction of adrenal cortex
  • Suppression of ACTH by high therapeutic doses of glucocorticoids
  • Infection
  • Tumor invasion
  • Adrenal infarction
97
Q

What is the disease that is the primary cause of adrenocortical hypo secretion?

A

Addison’s disease

98
Q

What is Addison’s disease?

A

Primary insufficiency of adrenal gland, autoimmune disease where the antibodies block the ability to secrete corticosteroids and destroy the gland

99
Q

What do adrenal cells look like with adrenocortical hypo secretion?

A

Anytime the tissue is damaged or cells are killed off - invading malignant cells can take over the function of normal cells

100
Q

What are the symptoms of Addison’s disease?

A
  • Weakness
  • Fatigue
  • Anorexia
  • Hyperpigmentation of skin
101
Q

Why does Addison’s disease present with hyper pigmentation of the skin?

A

Stimulation of melanocytes

102
Q

What is secondary adrenocortical insufficiency?

A

Any disorder of the hypothalamus and pituitary gland that reduces the output of ACTH

103
Q

What are some examples of causes of secondary adrenocortical insufficiency?

A
  • Metastatic cancer
  • Infection
  • Infarction
  • Irradiation
104
Q

What are the symptoms of secondary adrenocortical insufficiency?

A

Same as Addison’s disease, except without hyper pigmentation of the skin

  • Weakness
  • Fatigue
  • Anorexia
105
Q

Why are cortisol and ACTH levels difficult to interpret?

A

Due to effects of stress and sleep cycle variations

106
Q

What kind of tests do we use to evaluate cortisol and ACTH?

A

Instead, we evaluate cortisol and ACTH response to physiologic factors - don’t just test their amount, we test their function too

107
Q

What does cortisol bind to in the blood?

A

Cortisol binding globulin (CBG)

108
Q

When is plasma cortisol level highest?

A

Morning at 8 am

109
Q

When is the plasma cortisol level the lowest?

A

Evening at 11 pm

110
Q

What does free urine cortisol measure?

A

Degree to which plasma cortisol exceeds protein binding capacity (amount of cortisol not bound to protein)

111
Q

What time of the day is cortisol measured?

A

8 am

112
Q

What are two precursors to cortisol that can be measured?

A

17 hydroxysteroids

17 Ketosteroids

113
Q

With what disorders might we measure precursor levels to cortisol?

A

When trying to establish diagnosis of congenital adrenal hyperplasia or adrenal carcinoma

114
Q

What is DHEA-S?

A

The major androgen produced by the adrenal gland

115
Q

Which of the three categories of adrenal hormones is DHEA?

A

Gonadocorticoid

116
Q

Why do we measure DHEA?

A

It is an easy measurement of adrenal production activity levels

117
Q

What is a dexamethasone suppression test?

A

Patient is given a dose of dexamethasone which should suppress ACTH production and decrease cortisol

118
Q

What does dexamethasone mimic?

A

Mimics cortisol - if dexamethasone (cortisol) levels increase, the feedback system tells the anterior pituitary to decrease ACTH production

119
Q

What hormone is measured using a dexamethasone suppression test?

A

Measure ACTH before and after administration of dexamethasone - ACTH should decrease after administration

120
Q

What is a cortrosyn stimulation test?

A

Uses synthetic bioactive ACTH to test adrenal cortisol producing ability

121
Q

What hormone is measured using a cortrosyn stimulation test?

A

Measure cortisol levels - should increase when given synthetic ACTH

122
Q

What gland experiences a problem with Cushing’s disease?

A

Anterior pituitary

123
Q

What are the lab findings of Cushing’s disease?

A
  • Increased ACTH

- Increased urine free cortisol

124
Q

What would happen during a dexamethasone suppression test in a patient with Cushing’s disease?

A

Failure to suppress cortisol levels - anterior pituitary doesn’t care that there is excess “cortisol,” and never decreases ACTH

125
Q

What are the lab findings of Cushing’s syndrome?

A
  • Increased urine free cortisol levels

- Decreased ACTH

126
Q

Why does ACTH decrease with Cushing’s syndrome?

A

The adrenal cortex is pumping out cortisol regardless of ACTH levels - the anterior pituitary attempts to depress it by decreasing it’s ACTH levels

127
Q

What are the lab findings with adrenal insufficiency (Addison’s disease)?

A
  • Increase ACTH
  • Decrease plasma and urine cortisol levels
  • Cortrosyn stimulation test produces no increase in cortisol levels
    (- Secondary cases will show decreased ACTH as well as decreased cortisol)

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