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endocrine pathology + medicine > endocrine-thyroid > Flashcards

endocrine-thyroid Flashcards

1
Q

Where is the thyroid gland located?

A

Anterior and caudal to the cartilages of the larynx

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2
Q

What is its origin?

A

thyroglossal duct

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3
Q

Weight ?

A

20-25g (depending on body size and iodine supply)

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4
Q

Describe the morphological features of the thyroid gland

A

It consists of two lateral lobes(4cm in length) joined by an isthmus.
It is comprised of spherical follicles that vary in size. These follicles are lined by cuboidal epithelial cells/ follicular epithelium and has an inner colloid lumen. Parafollicular cells also present i.e C cells that produce calcitonin

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5
Q

What is the functional unit of the thyroid?

A

follicles- site of formation and secretion of thyroid hormones

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6
Q

Describe how thyroid hormones are formed

A

Tyrosine residue of thyroglobulin ( which is located in colloid ; serves to gather thyroid hormone within the follicular lumen) becomes iodinated. This then forms DIT and MIT which combine to form 2 biologically active thyroid hormones- T3 (triiodothryonine; most active) and T4 (thyroxine). The enzyme for this process of thyroid peroxidase (TPO)

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7
Q

What are other functions of thyroglobulin?

A

It serves as a storage for iodine and excess thyroid hormone for secretion at a steady state or on demand

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8
Q

What are some developmental anomalies a/w thyroid gland?

A

Hypoplasia/aplasia- rare
Thyroglossal duct cyst-Thyglossal duct is a path for descent of thyroid from tongue to its location in neck. The cyst dies out normally; if it persists, it may cause cystic dilation and seen as anterior neck mass.
-Heterotopic thyroid tissue

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9
Q

What are the general functions of the thyroid hormones?

A

TARGETS EVERY TISSUE
Required for homeostasis of all cells
Influence cell differentiation, growth, and metabolism

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10
Q

What are the thyroid function tests?

A 
Free T4
Total T3
TSH
Thyroid antibodies 
-antibodies to TPO, thyroglobulin, TSH receptor
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11
Q

What are the carrier proteins that the thyroid hormones bind to in the blood?

A

transthyretin, albumin, thyroxine binding globulin

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12
Q

What is the typical presentation in hypothyroidism?

A

low T3, low T4, high TSH (to overcompensate for low thyroid hormone)

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13
Q

Typical presentation of hyper thyroidism?

A

high T4, low TSH (-ve feedback)

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14
Q

What is the presentation of iodine deficiency

A

enlargement of gland

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15
Q

What are iodine sources?

A

iodised table salt, milk, cheese, eggs and fish

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16
Q

What are the primary causes of hyperthyroidism?

A 
Graves disease (most common) 
multinodular goitre
functioning adenoma
functioning carcinoma
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17
Q

What is the secondary cause of hyperthyroidism

A

ACTH releasing adenoma (of pituitary) - thyrotropic adenoma - RARE

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18
Q

What are OTHER causes of hyperthyroidism?

A

Thyroiditis
Exogenous thyroid
stuma ovarii - ovarian TERATOMA with ectopic thyroid
iodine and iodine containing drugs- amiodarone and contrast agents

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19
Q

What are the symptoms of hyperthyroidism?

A 
Constitutional
•Heat intolerance
•Weight loss despite increased appetite
CVS
•Tachycardia
•Palpitations
GIT
•Hypermotile symptoms
NS
•Tremor
•Irritability
•Often proximal muscle weakness

Also in regard to eye - lid lag, retraction and stare ; this is due to increased adrenergic tone to levator palpebrae muscles

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20
Q

What is thyroid storm

A

acute, life threatening condition characterised by excess thyroid hormone release
usually occurs in underlying Grave’s

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21
Q

What are the causes of thyroid storm?

A 
Sepsis
Surgery
DKA
Trauma
Radioactive Iodine
Anaesthesia 
Drugs- NSAIDS, salicylates
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22
Q

What is the treatment for thyroid storm?

A 
Resuscitation 
Paracetamol/Ice
High dose PTU
Corticosteroids
Electrolytes
Iodine compounds
Antiadrenergics
Surgery(1 week)
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23
Q

What are the thyroiditis a/w hyperthyroidism

A

Subacute viral thyroiditis (De Quervain’s) - occurs in females more ; 30-50; following a viral infection/ inflam process(focal acute inflam/granulomatous); pain in neck (esp when swallowing) variable enlargement of gland ; systemic symptoms; fever , malaise ; self limiting and returns to euthyroid state in 6-8weeks

Silent thyroiditis
typically seen in middle aged pregnant women(post partum thyroiditis); autoimmune cause; circulating autoantibodies to thyroid; presents as PAINLESS mass in neck and elevated thyroid hormone: euthyroid state in few months

Riedel's thyroditis: 
rare 
chronic fibrotic, infiltrative 
''woody'' 
thoracic inlet obstruction
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24
Q

Why does thyroiditis cause hyperthyroidism?

A

It causes elevated thyroid hormone level because the inflammatory process destroys follicles causing a release of thyroid hormone. This may be followed by hypothyroidism

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25
Q

What is another name for Grave’s disease? and what are the micro/macro findings?

A

True Grave’s Opthalmopathy
macro- diffuse enlargement of thyroid due to hyperplasia and hypertrophy of follicles

micro; star shaped follicles, little colloid, increased lymphocytes

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26
Q

What causes Grave’s disease?

A

Due to thyroid autoAb’s that cross-react w/ Ag’s in fibroblasts, adipocytes, myocytes behind the eyes

occurs in females , 15-40, familial tendency

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27
Q

What are the signs and symptoms of Graves disease

A

Besides enlarged goitre with bruit

Proptosis, diplopia, inflammatory changes
i.e conjunctival infection, chemosis, periorbital oedema

Extremities:
Grave’s dermopathy (pretibiial myxoedema)
thickening and reddening of dermis due to lymphocytic infiltration

Graves acropachy-soft tissue swelling of the hands and clubbing of fingers

oncholysis- painless separation of the nail from the nail bed

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28
Q

What are the causes of worsening ophthalmopathy

A 
Pre-existing eye disease
Smoking
marked ↑ T3
marked ↑ TSI titers
Not letting pt get to hypothyroid state following 131-RAIA.
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29
Q

Explain (Solitary) thyroid nodule

A

discrete thyroid lesion
>1cm require investigation
presents w enlarged nodes and hoarseness
occurs in 4-8% of population

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30
Q

How do we differentiate from all the causes of hyperthyroidism?

A

History and clinical examination

  • Symptoms and signs, age
  • Family history, autoimmune diseases
  • Medications, recent contrast investigations

TPO/ TSH-receptor antibodies

Thyroid scintigraphy

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31
Q

In regards to scintigraphy, what do you expect to see in Grave’s disease, Toxic nodular goitre and Thyroiditis

A

Graves disease- diffuse uptake
Nodular goitre- focal uptake
Thyroiditis- absent/reduced uptake

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32
Q

In regard to anti thyroid autoantibodies, are they present or absent in Grave’s disease, Toxic nodular goitre and Thyroiditis

A

Graves- present
Toxic nodular goitre-absent
Thyroiditis- present(silent), absent(subacute viral )

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33
Q

Treatment for Graves Disease

A 
Medical
Beta blocker for symptoms
Carbimazole
Propylthiouracil (PTU)
Radioactive iodine (c/i in SEVERE graves ophthalmopathy)

Surgery
Thyroidectomy
Subtotal thyroidectomy
Patient should be euthyroid prior to surgery to decrease vascularity of gland.

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34
Q

What are the investigations for (solitary) nodule?

A

If >1cm U/S w/ FNA , if <1cm no FNA
if no malignancy from FNA, retake in 6 months
U/s confirms if solitary/multinodular, cystic/solid,calcifications,size,vascularity
Scintigraphy- hot nodules unlikely to be cancer; uptake of technetium
cold nodules- 10% chance cancer
CT neck

This is all done after a proper history/physical (Clinical) is taken where TSH levels are measured and if high/normal result given

Clinical:
history, change in lesion size, blood tests, clinical evaluation

35
Q

What do you do if the pt has a thyroid nodule >1cm on palpation and imaging but a low TSH?

A

Scan I123, Tc99; radionuclide scan ;; cold/hot

36
Q

What are the risk factors for carcinoma a/w the presence of thyroid nodules?

A
  • solitary thyroid nodule <30, >60
  • irradiation of neck as an infant and adolescent
  • symptoms of pain or pressure and voice change , or RAPIDLY ENLARGING nodule
37
Q

What is mild / subclinical hyperthyroidism

A

where one has normal TT3/FT4 and low/undetectable TSH

38
Q

What are the causes of subclinical hyperthyroidism?

A

Graves
exogenous LT4 therapy- most common
isolated contrast
autonomously functioning nodule

39
Q

What are pts at risk of in subclinical hyperthyroidism?

A

older pts at risk of osteoporosis and atrial fibrillation

40
Q

How do pts present with subclinical hyperthyroidism? When is appropriate to treat?

A

euthyroid, only treat when TSH <0.1

41
Q

List all the pharmacalogical agents for hyperthyroidism.

A
  1. Thyroid hormone synthesis inhibitors
    Carbimazole/Methimazole
    Propylthiouracil
    Inhibit thyroid hormone synthesis. SEs: rash, rare: agranulocytosis
  2. Thyroid hormone secretion blockade (mainly in preparation for surgery)
    a. Iodides (Lugols iodine, SSKI, iopanoic acid )
  3. Beta-adrenergic blockers
    a. Propanolol
  4. Corticosteroids (for severe thyroiditis)
  5. Radioactive iodine therapy- I -131; Gamma and Beta Particles
    - toxic nodular disease
    c/i in pregnant and active Grave’s opthalmopathy
42
Q

What are the causes of HYPOthyroidism?

A

congenital
agenesis of thyroid
defect in thyroid hormone production due to enzymatic defect

destructive effect on thyroid gland due to
Hashimoto’s thyroiditis
radiation
thyroidectomy
infiltrative diseases like haematochromastosis

others’:
drugs that have antithyroid effects- lithium, iodine, iodine containing contrast/drugs , IFA

Secondary causes
deficient secretion of TSH due to craniopharyngioma or pit tumor

43
Q

What are the symptoms of hypothyroidism?

A 
Adult onset
•Apathy
•Mental sluggish
•Cold intolerance
•‘Oedema’ of face, tongue and some viscera
•Hoarse
•‘Myxoedema’
•NB: Elderly
Childhood onset
•Same as for adults but also:
•Impaired skeletal development
•Mental retardation
•‘Cretinism’-stunted physical and mental growth
44
Q

Treatment for hypothyroidism?

A

Levo-thyroxine, maintenance dose ranges from 50-200 mcgs daily titrated against TSH.
In severe hypothyroidism, dose ~ 1.6 mcg/kg/day

“Start low and go slow “ in the elderly and those with heart disease.

In secondary hypothyroidism, exclude or treat adrenal insufficiency first, aim is to keep T4 in the middle of the normal range, ignore TSH.

45
Q

Subclinical hypothyroidism?

A

Mild/early Thyroid Failure
Normal Free T4 but persistently raised TSH
Treated if TSH > 10
TSH 4-10 , treatment of questionable benefit

46
Q

What are the causes of thyroid enlargement?

A

-simple/ multinodular goitre
-nodules due to hyperplasia, cyst,neoplasm
some cases of thyroiditis

47
Q

Pathogenesis of simple/multinodular goitre(MNG) (i.e diffuse involvement of gland)

A

Low iodine - endemic/nonendemic cause
Other non endemic causes: female gender, synthesis defect -> decreased T3/T4 output-> increased TSH (no -ve feedback) -> hyperplasia/hypertrophy of follicle (simple goitre) -> atrophy, fibrosis, haemosiderin, hyperplasia/hypertrophy (MNG)

48
Q

Features of hashimoto’s Thyroiditis

A
  • Middle age, F>M
  • Chronic thyroiditis
  • Autoimmune – attacked by cytotoxic T lymphocytes
  • Clinically: Euthyroid / hypothyroid, uncommonly hyperthyroid (Hashitoxicosis)
49
Q

Macro and micro of hashimotos

A

macro- swollen at start, atrophy later

micro- lymphocytic infitration of stroma w reactive germinal centres and oxyphilic change of follicular epithelium

50
Q

What are the categories of Thyroid FNA?

A
  • Thy 1 – Non diagnostic
  • Thy 2 – Non neoplastic
  • Thyroiditis, hyperplastic nodule, colloid nodule
  • Thy 3 – Neoplasm possible
  • Follicular lesion (Thy 3f) – hyperplastic nodule, follicular neoplasm.
  • Atypia (Thy 3a)
  • Thy 4 – Suspicious of malignancy
  • Thy 5 – Malignant
51
Q

If person diagnosis with Thy2 colloid nodule, what is the next step?

A
  • Repeat U/S and or FNA
52
Q

If person has a follicular lesion, what is the Thyroid FNA category and how is this managed?

A

Thy3f , excision

53
Q

What is the thyroid FNA category if malignancy is present? How is this managed?

A

Thy4/5, excision

54
Q

Classify thyroid neoplasms

A

Benign
follicular adenoma
others like lipoma

Malignant 
Papillary carcinoma (80%) 
Follicular carcinoma (10%)
Medullary carcinoma(<5%)
Anaplastic carcinoma (1-2%)

mets, lymphoma

55
Q

Features of follicular adenomas

A
  • Any age F>M
  • Clinical
  • euthyroid, sometimes toxic
  • Macro
  • Encapsulated, firm
  • Usually <5cm
  • Micro
  • Follicles of rather uniform size
  • Variable colloid
  • Can show cytological atypia
  • NO capsular or vascular invasion
56
Q

What are the other variants of follicular adenoma?

A

Hurthlecell adenoma and atyical adenoma

57
Q

Malignant thyroid tumours occur more in male or females ?

A

Females

58
Q

What predisposes one to malignant thyroid tumors?

A

genetic(men syndrome)
radiation exposure
adenoma
hashimotos

59
Q

What is the prognosis for papillary ca

A

good; 98% 5 year survival

60
Q

What is the age range that papillary ca occur in?

A

20-40 females

61
Q

Describe the pathology aw papillary ca

A

Usually multifocal
slow growing tumour
macro:
small whitish nodule with or without cystic spaces

micro: 
papillary architecture
nuclear inclusions
nuclear grooves
psammoma bodies 
clear nuclei-'orphan annie'
62
Q

Any invasion occurs in papillary carcinoma?

A

Propensity for invading lymphatics

regional lymph node mets

63
Q

List the variants of papillary carcinoma

A 
•Follicular variant
•Oncocytic variant
•Columnar variant
•Diffuse sclerosing variant
•Tall cell variant
•Papillary microcarcinoma
<1cm
Common
Incidental finding
64
Q

Treatment for papillary carcinoma?

A 
total thyroidectomy >1cm 
lobectomy <1cm 
and Lateral Neck/ central neck   dissection 
radioactive iodine ablation 
lifelong eltroxin
65
Q

When and why is L thyroxine given?

A

post operation to suppress TSH

66
Q

What age does follicular carcinoma usually occur?

A

50-60 females

67
Q

Features of follicular carcinoma

A

slowly enlarging painless thyroid nodule

micro: capsular,vascular invasion

68
Q

Does spread occur w follicular carcinoma?

A

haematogenous spread- bone marrow

69
Q

Prognosis of follicular carcinoma

A

dependent on degree of invasion
minimally invasive- 95% survival
widely invasive- 30-70% 5 yr survival

70
Q

Treatment for follicular car

A 
total thyroidectomy >1cm + radioactive iodine abalation
total lobectomy (w/o mets) 
thyroid hormone (Eltroxin) after surgery
71
Q

Define medullary car

A

Neuroendocrine neoplasm of parafollicular Ccells which secrete calcitonin
slow growing

72
Q

What age group does medullary car occur in?

A

50-60 years

73
Q

What is the % a/w genetic factors in medullary car

A

20-25% familial / MEN 2

74
Q

When does anaplastic carcinoma occasionally happen?

A

elderly females

75
Q

How does anaplastic car present?

A

aggressive and rapid growth

  • pressure symptoms (oesophagus and trachea)
  • laryngeal nerve paralysis
76
Q

Any mets occur in anaplastic car?

A

LN, lungs, bone

77
Q

Differential diagnosis for anaplastic car

A

Rieldel’s thyroiditis due to macro appearance being hard and gritty

78
Q

Micro appearance of anaplastic car

A

undifferentiated giant cells

79
Q

What is the prognosis for anaplastic car

A

poor prognosis; usually fatal within 1 year

chemo and radio not effective ; complete resection not possible

80
Q

What are the complications of thyroid surgery?

A

Hypo-parathyroidism

Recurrent Laryngeal Nerve Damage

Haemorrhage / Haematoma

Infection

Recurrence

Thyroid Storm

81
Q

Describe thyroid lymphoma

A

Uncommon

Associated with Hashimoto’s thyroiditis

Occurs commonly in the 5th decade of life

Very responsive to chemo-radiation

82
Q

When is surgery for hyperthyroidism indicated?

A

Patient choice
When Radioactive iodine c/i
obstructive/diffuse goitre
single toxic adenoma

83
Q

What are the advantages and disadvantages of RAI?

A

Advantages

75% cure at 2-3 months
Repeated for 25% who don’t respond
90% cure rate
Easily tolerated
Inexpensive

Disadvantages

Hypothyroidism
Pregnancy
Breastfeeding
Young patients
Low RAI uptake
Radiation thyroiditis
Cancer risk

endocrine pathology + medicine (4 decks)

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