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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
Q

What are the two most common cause of primary hypothyroidism

A

Hashimoto’s thyroiditis

Iodine deficiency

26
Q

What is the most common cause of primary hypothyroidism in the developed world

A

Hashimoto’s thyroiditis

27
Q

What is the most common cause of primary hypothyroidism in the developing world

A

Iodine deficiency

28
Q

Where is the site of pathology in secondary hypothyroidism

A

Pituitary gland

29
Q

Define Hashimoto’s thyroiditis

A

Most common cause of primary hypothyroidism

Characterised by chronic autoimmune thyroiditis cell and antibody mediated processes cause destruction of the thyroid gland.

30
Q

What are the two antibodies are associated with Hashimoto’s thyroiditis

A

Antithyroid peroxidase (anti-TPO) antibodies

Antithyroglobulin antibodies

31
Q

What are two risk factors for Hashimoto’s thyroiditis

A

Female

Increase in age

32
Q

Why is iodine deficiency a cause of primary hypothyroidism

A

Iodine is a key component of thyroxine

Thus deficiency causes impaired production of thyroxine

33
Q

How do we prevent iodine deficiency in developed world

A

Iodine is added to foods such as table salt

34
Q

What would be the biochemistry results characteristic of secondary hypothyroidism

A

High TRH

Low TSH (due to lack of TSH production)

Low T3/T4

35
Q

Name two most common causes of secondary hypothyroidism

A

Pituitary adenomas

Radiation

36
Q

What is the site of pathology for tertiary hypothyroidism

A

Hypothalamus or hypophyseal portal system

37
Q

What would be the biochemistry results characteristic of tertiary hypothyroidism

A

Low TRH

Low TSH

Low T3/T4

38
Q

What is postpartum thyroiditis

A

Transient change that occurs in the six months following birth, it may be preceded by a period of hyperthyroidism

39
Q

What is Amiodarone-induced hypothyroidism

A

Amiodarone is an anti-arrhythmic drug with a high iodine content.

May cause both hypothyroidism and hyperthyroidism.

40
Q

Name some of the symptoms of hypothyroidism

A
  • Fatigue
  • Lethargy
  • Weight gain
  • Cold intolerance
  • Menstrual irregularities (oligomenorrhoea, amenorrhoea, menorrhagia)
  • Reduced libido
  • Goitre
  • Constipation
41
Q

Name some of the signs of hypothyroidism

A
  • Hair loss (characteristically the outer third of the eyebrows)
  • Dry skin
  • Goitre
  • Delay tendon reflexes
  • Bradycardia
42
Q

Define Oligomenorrhoea

A

Infrequent menstrual periods

43
Q

Define amenorrhoea

A

Absence of menstruation

44
Q

Define menorrhagia

A

Heavy/prolonged menstrual periods

45
Q

How is hypothyroidism diagnosed

A

A diagnosis is based on TSH thyroid profile test

Supplemented fT4 thyroid profile test

46
Q

What investigation is the most sensitive and specific for diagnosing primary hypothyroidism

A

TSH blood test

47
Q

What investigation is the most useful to quantify the degree of hypothyroidism

A

fT4 blood test

48
Q

Anti-thyroglobulin (Anti-Tg) antibodies are commonly elevated in which specific hypothyroidism condition

A

Hashimoto’s thyroiditis

49
Q

Name the two autoantibodies that can be tested for as part of the make up of hypothyroidism

A

Anti-thyroid peroxidase (anti-TPO) antibodies

Anti-thyroglobulin (Anti-Tg) antibodies

50
Q

Which autoantibody is most specific and sensitive for Hashimoto’s thyroiditis

a) Anti-thyroid peroxidase (anti-TPO) antibodies
b) Anti-thyroglobulin (Anti-Tg) antibodies

A

b) Anti-thyroglobulin (Anti-Tg) antibodies

anti-TPO antibodies are non-specific and can also be elevated in conditions like Graves’ disease

51
Q

What is the mainstay of treatment for hypothyroidism

A

Thyroid hormone replacement with oral levothyroxine

52
Q

What is levothyroxine

A

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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