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ENDOCRINE > Clinical Thyroid Disease > Flashcards

Clinical Thyroid Disease Flashcards

1
Q

starting in the hypothalamus and ending in peripheral tissues, briefly outline the path taken to release TH

A

Hypothalamus releases TRH - acts on the anterior pituitary which releases TSH - acts on thyroid gland which produces T3 and T4 - travels in blood stream to act on peripheral tissues

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2
Q

what keeps the hormone levels in a tight range

A

negative feedback control

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3
Q

what is hypothyroidism

A

when the thyroid is under active - i.e. does not produce enough TH

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4
Q

what is hyperthyroidism

A

when the thyroid is over active - i.e. produces too much TH

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5
Q

what are some typical symptoms of hypothyroidism

A

symptoms associated with low metabolism e.g.:

  • weight gain
  • lethargy/fatigue
  • feeling cold
  • constipation
  • heavy periods
  • dry skin/hair
  • bradycardia
  • slow reflexes
  • low mood
  • GOITRE

severe = puffy face, large tongue, hoarseness, coma

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6
Q

what are some typical symptoms of hyperthyroidism

A

symptoms associated with high metabolism e.g.:

  • weight loss
  • anxiety/irritability
  • heat intolerance
  • increased bowel frequency
  • light periods
  • sweaty palms
  • palpitations
  • hyperreflexia/tremors
  • GOITRE
  • thyroid eye symptoms/signs
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7
Q

what would the TSH and FT4&3 levels be like in PRIMARY hypothyroidism

A

raised TSH

low FT4&3

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8
Q

what would the TSH and FT4&3 levels be like in SUBCLINICAL hypothyroidism

A

raised TSH

normal FT4&3

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9
Q

what would the TSH and FT4&3 levels be like in SECONDARY hypothyroidism

A

low TSH

low FT4&3

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10
Q

what occurs in subclinical hypothyroidism to explain normal levels of FT4&3

A

also known as compensated hypothyroidism - thyroid gland can raise TSH enough on its own to make levels of FT4&3 normal even though TSH levels are elevated

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11
Q

what area is affected in primary hypothyroidism

A

the thyroid - causes can be autoimmune (hashimoto’s) or iodine deficiency in the diet

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12
Q

what area is affected in secondary hypothyroidism

A

the anterior pituitary

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13
Q

what is the prevalence of hypothyroidism in men and women

A

men - 0.1%

women - 1.9%

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14
Q

prevalence of congenital hypothyroidism

A

1 in 3500 births

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15
Q

what are the cases of primary Hypo

A
  1. congenital

2. acquired

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16
Q

what are the different causes of congenital primary hypo

A
  1. developmental - agencies/maldevelopment
  2. dyshormonogenesis - trapping/organification/dehalogenase

cretin = someone who is untreated for primary hypo from birth

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17
Q

what are the different causes of acquired primary hypo

A
  1. autoimmune thyroid disease
    - Hashimotos
    - atrophic
  2. Iatrogenic
    - post op/radioactive iodine
    - external RT for head/neck cancers
    - antithyroid drugs, amiodrone, lithium, interferon
  3. chronic iodine deficiency
  4. post subacute thyroiditis
    - post partum thyroiditis
18
Q

what re the causes of secondary/tertiary hypothyroidism

A

pituitary/hypothalamic damage

  • pituitary tumour
  • craniopharyngioma
  • post pituitary surgery/radiotherapy
  • sheehans syndrome
  • isolated TRH deficiency
19
Q

what is sheehans syndrome

A

when a woman has a massive post part haemorrhage - can lead to hypothyroidism

20
Q

what are the 2 main investigations for hypothyroidism

A
  1. TSH/FT4 levels in the blood

2. Autoantibodies - TPO (thyroid peroxidase antibodies)

21
Q

what are other indicators to look for in hypothyroidism

A
  • in a FBC - MCV raised (macrocytic anaemia)
  • lipids - hypercholesterolaemia
  • hyponatremia due to SIADH
  • increased muscle enzymes, ALT, CK
  • hyperprolactinaemia
22
Q

what is the main treatment for hypothyroidism

A
  1. levothyroxine (T4 substitute) tablets

2. liothyronine (T3)

23
Q

how is levothyroxine given

A

initial dose 50micrograms/day

  • increase after 2 weeks to 100 micrograms
  • increase dose until TSH normal (or FT4 in normal range in secondary)
24
Q

when should you review a patient on levothyroxine

A

2 months after starting

- annual testing once stabilisation of TSH met

25
Q

what are special situations that call for a change in treatment and how would you treat them

A
  1. ischaemic heart disease - start lower dose (25mcg) and increase cautiously - RISK OF PRECIPITATING ANGINA
  2. pregnancy - patients need increase in LT4 dose
  3. Postpartum thyroiditis - trial withdrawl and measure TFTs in 6 weeks
  4. myxedema coma - very rare emergency, may need IV T3 (steroid)
26
Q

when would you treat subclinical hypo

A
  1. consider treatment when TSH >10
  2. TSH > 5 with positive thyroid antibodies
  3. TSH elevated with symptoms - trial therapy for 3/4 months - continue if symptomatic improvement
27
Q

what are the risks of over treatment

A
  • osteopenia
  • atrial fibrillation
  • excitability
28
Q

what is goitre

A

the enlargement of the thyroid gland - swollen neck

29
Q

what are the cases of goitre

A
  1. physiological - puberty/pregnancy
  2. autoimmune
  3. thyroiditis
  4. iodine deficiency
  5. dyshormogenesis
  6. goitrogens - eg cabbage
30
Q

what are the different types of goitre

A
  1. multinodular
  2. diffuse - colloid, simple
  3. cysts
  4. tumours - ademona, carcinoma, lymphoma
  5. miscellaneous - sarcoidosis, tuberculosis
31
Q

when is a solitary nodule at risk of malignancy

A
  • in children
  • adults less than 30 or over 60
  • previous head and neck irradiation
  • pain, cervical lymphadenopathy

*large dominant nodule of MNG also needs investigation

32
Q

what are the investigations for a solitary thyroid nodule

A
  1. thyroid function tests (toxic nodule)
  2. isotope scanning (hot nodule)
  3. Ultrasound - differentiating malignant from benign
  4. Fine needle aspiration
  5. X-rays
33
Q

what is a hot nodule

A

an autonomous functioning nodule - on isotope scan shows up bright = area of activity - i.e. iodine isotope uptake normal, TSH doing its job

34
Q

what is a cold nodule

A

a non-funtioning thyroid nodule - ie a cyst or part of gland that is not taking up anything

35
Q

what are the 5 types of thyroid cancer

A

MAIN ONES:

  1. papillary
  2. follicular

OTHER:

  1. anaplastic
  2. lymphoma
  3. medullary
36
Q

what are the features of papillary thyroid cancer

A
  1. most common
  2. multifocal, local spread to lymph nodes
  3. good prognosis
37
Q

what are the features of follicular thyroid cancer

A
  1. usually single lesion
  2. metastases to lung/bone
  3. good prognosis if resectable
38
Q

what are the features of anaplastic thyroid cancer

A
  1. <5% of thyroid cancers
  2. aggressive, locally invasive
  3. very poor prognosis
  4. does not respond to radio iodine BUT external RT may help briefly
39
Q

what are the features of lymphoma

A
  1. rare
  2. may arise from preexisting hashimotos thyroiditis
  3. external RT more helpful, combined with chemotherapy
40
Q

what are the features of medullary thyroid cancer

A
  1. tumour arising from parafollicular C cells
  2. often associated with MEN 2
  3. serum calcitonin levels raised
  4. total thyroidectomy needed, no role for radio iodine
  5. variable prognosis
41
Q

what factors make prognosis poorer

A
  1. age - <16 or >45
  2. tumour size
  3. spread outside thyroid capsule
  4. metastases
  5. TNM stage
42
Q

what is the treatment for process for thyroid cancer

A
  1. near total thyroidectomy - remove everything you can including associated lymphs
  2. ablative therapy - radioactive iodine - gets easily picked up by thyroid
  3. long term thyroxine to suppress tumour - “puts tumour to sleep” - doesn’t need to “wake up” and produce hormone as hormone levels synthetically high enough

ENDOCRINE (13 decks)

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