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Finals: Medicine > Hypothyroidism > Flashcards

Hypothyroidism Flashcards

1
Q

Define hypothyroidism

A

Refers to inadequate output of thyroid hormones by the thyroid gland

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2
Q

Hypothalamic-pituitary-thyroid axis is made up of TRH, TSH, T3 and T4 hormones.

What does TRH stand for

A

Thyrotropin releasing hormone

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3
Q

Thyrotropin releasing hormone (TRH) is secreted by?

A

Secreted from the paraventricular nucleus of the hypothalamus

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4
Q

Thyrotropin releasing hormone (TRH) is secreted from the paraventricular nucleus of the hypothalamus and travel to the anterior pituitary via what?

A

Hypophyseal portal system

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5
Q

What is the function of Thyrotropin releasing hormone (TRH)

A

Stimulates the release of thyroid stimulating hormone (TSH) from the anterior pituitary

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6
Q

What produces Thyroid stimulating hormone (TSH)

A

The thyrotrophs of the anterior pituitary,

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7
Q

What hormone stimulates the release of Thyroid stimulating hormone (TSH)

A

Thyrotropin releasing hormone (TRH) from the hypothalamus

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8
Q

Thyroid stimulating hormone (TSH) is transported to the thyroid gland by?

A

In the blood

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9
Q

What is the function of Thyroid stimulating hormone (TSH)

A

Acts upon the thyroid gland promoting the synthesis and release of thyroid hormone

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10
Q

Name the hormone produced by the hypothalamus used in the hypothalmic-pituitary-thyroid axis

A

Thyrotropin releasing hormone (TRH)

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11
Q

Name the hormone produced by the anterior pituitary used in the hypothalmic-pituitary-thyroid axis

A

Thyroid stimulating hormone (TSH)

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12
Q

Is it the anterior or posterior pituitary that produces Thyroid Stimulating Hormone (TSH)

A

Anterior pituitary

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13
Q

Name the two thyroid hormones

A

Thyroxine (T4)

Triiodothyronine (T3)

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14
Q

Which thyroid hormone is more biologically active than its counterpart

A

T3 is more biologically active than T4

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15
Q

What thyroid hormone is produced at a higher amount

A

90% of the secreted thyroid hormone is T4; only 10% is T3

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16
Q

Which thyroid hormone is periperally converted to its counterpart

A

Periperally, T4 is converted to T3

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17
Q

How are thyroid hormones transported in the blood

A

T3 and T4 are highly lipophilic and thus bind to thyroxine-binding globulin (TBG) in the blood

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18
Q

T3 and T4 act on what kind of receptors

A

Intracellular receptors

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19
Q

What are the four major effects of thyroid hormone

A
  1. Increases the basal metabolic rate
  2. Growth: increases release and effect of GH and IGF-1.
  3. Cardiovascular: increases the heart rate and contractility through increasing sensitivity to catecholamines.
  4. Complete a negative feedback loop through the suppression of TRH and TSH release.
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20
Q

Complete these parts of the hypothalamic-pituitary-thyroid axis

A
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21
Q

What are the 3 types of hypothyroidism

A

Primary

Secondary

Tertiary

22
Q

Where is the site of pathology in primary hypothyroidism

A

Disease is intrinsic to the thyroid gland

23
Q

What would be the biochemistry results characteristic of primary hypothyroidism

A

High TSH

Low T3/T4

24
Q

What would be the biochemistry results characteristic of subclinical hypothyroidism

A

High TSH

Normal T3/T4

25
What are the two most common cause of primary hypothyroidism
Hashimoto’s thyroiditis Iodine deficiency
26
What is the most common cause of primary hypothyroidism in the developed world
Hashimoto’s thyroiditis
27
What is the most common cause of primary hypothyroidism in the **developing** world
Iodine deficiency
28
Where is the site of pathology in secondary hypothyroidism
Pituitary gland
29
Define Hashimoto’s thyroiditis
Most common cause of primary hypothyroidism Characterised by chronic autoimmune thyroiditis cell and antibody mediated processes cause destruction of the thyroid gland.
30
What are the two antibodies are associated with Hashimoto's thyroiditis
Antithyroid peroxidase (anti-TPO) antibodies Antithyroglobulin antibodies
31
What are two risk factors for Hashimoto's thyroiditis
Female Increase in age
32
Why is iodine deficiency a cause of primary hypothyroidism
Iodine is a key component of thyroxine Thus deficiency causes impaired production of thyroxine
33
How do we prevent iodine deficiency in developed world
Iodine is added to foods such as table salt
34
What would be the biochemistry results characteristic of secondary hypothyroidism
High TRH Low TSH (due to lack of TSH production) Low T3/T4
35
Name two most common causes of secondary hypothyroidism
Pituitary adenomas Radiation
36
What is the site of pathology for tertiary hypothyroidism
Hypothalamus or hypophyseal portal system
37
What would be the biochemistry results characteristic of **tertiary** **hypothyroidism**
Low TRH Low TSH Low T3/T4
38
What is postpartum thyroiditis
Transient change that occurs in the six months following birth, it may be preceded by a period of hyperthyroidism
39
What is Amiodarone-induced hypothyroidism
Amiodarone is an anti-arrhythmic drug with a high iodine content. May cause both hypothyroidism and hyperthyroidism.
40
Name some of the symptoms of hypothyroidism
* Fatigue * Lethargy * Weight gain * Cold intolerance * Menstrual irregularities (oligomenorrhoea, amenorrhoea, menorrhagia) * Reduced libido * **Goitre** * Constipation
41
Name some of the signs of hypothyroidism
* Hair loss (characteristically the outer third of the eyebrows) * Dry skin * Goitre * Delay tendon reflexes * Bradycardia
42
Define Oligomenorrhoea
Infrequent menstrual periods
43
Define amenorrhoea
Absence of menstruation
44
Define menorrhagia
Heavy/prolonged menstrual periods
45
How is hypothyroidism diagnosed
A diagnosis is based on TSH thyroid profile test Supplemented fT4 thyroid profile test
46
What investigation is the most sensitive and specific for diagnosing primary hypothyroidism
TSH blood test
47
What investigation is the most useful to quantify the degree of hypothyroidism
fT4 blood test
48
Anti-thyroglobulin (Anti-Tg) antibodies are commonly elevated in which specific hypothyroidism condition
Hashimoto’s thyroiditis
49
Name the two autoantibodies that can be tested for as part of the make up of hypothyroidism
Anti-thyroid peroxidase (anti-TPO) antibodies Anti-thyroglobulin (Anti-Tg) antibodies
50
Which autoantibody is most specific and sensitive for Hashimoto’s thyroiditis a) Anti-thyroid peroxidase (anti-TPO) antibodies b) Anti-thyroglobulin (Anti-Tg) antibodies
b) Anti-thyroglobulin (Anti-Tg) antibodies anti-TPO antibodies are non-specific and can also be elevated in conditions like Graves' disease
51
What is the mainstay of treatment for hypothyroidism
Thyroid hormone replacement with oral levothyroxine
52
What is levothyroxine
Synthetic version of T4, and metabolises to T3 in the body. The dose is titrated until TSH levels are normal.

Finals: Medicine (91 decks)

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