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endocrine pathology + medicine > endocrine-thyroid > Flashcards

endocrine-thyroid Flashcards

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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
What is another name for Grave's disease? and what are the micro/macro findings?
True Grave's Opthalmopathy macro- diffuse enlargement of thyroid due to hyperplasia and hypertrophy of follicles micro; star shaped follicles, little colloid, increased lymphocytes
26
What causes Grave's disease?
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
27
What are the signs and symptoms of Graves disease
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
28
What are the causes of worsening ophthalmopathy
``` Pre-existing eye disease Smoking marked ↑ T3 marked ↑ TSI titers Not letting pt get to hypothyroid state following 131-RAIA. ```
29
Explain (Solitary) thyroid nodule
discrete thyroid lesion >1cm require investigation presents w enlarged nodes and hoarseness occurs in 4-8% of population
30
How do we differentiate from all the causes of hyperthyroidism?
History and clinical examination - Symptoms and signs, age - Family history, autoimmune diseases - Medications, recent contrast investigations TPO/ TSH-receptor antibodies Thyroid scintigraphy
31
In regards to scintigraphy, what do you expect to see in Grave's disease, Toxic nodular goitre and Thyroiditis
Graves disease- diffuse uptake Nodular goitre- focal uptake Thyroiditis- absent/reduced uptake
32
In regard to anti thyroid autoantibodies, are they present or absent in Grave's disease, Toxic nodular goitre and Thyroiditis
Graves- present Toxic nodular goitre-absent Thyroiditis- present(silent), absent(subacute viral )
33
Treatment for Graves Disease
``` 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.
34
What are the investigations for (solitary) nodule?
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
What do you do if the pt has a thyroid nodule >1cm on palpation and imaging but a low TSH?
Scan I123, Tc99; radionuclide scan ;; cold/hot
36
What are the risk factors for carcinoma a/w the presence of thyroid nodules?
- 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
What is mild / subclinical hyperthyroidism
where one has normal TT3/FT4 and low/undetectable TSH
38
What are the causes of subclinical hyperthyroidism?
Graves exogenous LT4 therapy- most common isolated contrast autonomously functioning nodule
39
What are pts at risk of in subclinical hyperthyroidism?
older pts at risk of osteoporosis and atrial fibrillation
40
How do pts present with subclinical hyperthyroidism? When is appropriate to treat?
euthyroid, only treat when TSH <0.1
41
List all the pharmacalogical agents for hyperthyroidism.
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
What are the causes of HYPOthyroidism?
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
What are the symptoms of hypothyroidism?
``` 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
Treatment for hypothyroidism?
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
Subclinical hypothyroidism?
Mild/early Thyroid Failure Normal Free T4 but persistently raised TSH Treated if TSH > 10 TSH 4-10 , treatment of questionable benefit
46
What are the causes of thyroid enlargement?
-simple/ multinodular goitre -nodules due to hyperplasia, cyst,neoplasm some cases of thyroiditis
47
Pathogenesis of simple/multinodular goitre(MNG) (i.e diffuse involvement of gland)
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
Features of hashimoto's Thyroiditis
* Middle age, F>M * Chronic thyroiditis * Autoimmune – attacked by cytotoxic T lymphocytes * Clinically: Euthyroid / hypothyroid, uncommonly hyperthyroid (Hashitoxicosis)
49
Macro and micro of hashimotos
macro- swollen at start, atrophy later | micro- lymphocytic infitration of stroma w reactive germinal centres and oxyphilic change of follicular epithelium
50
What are the categories of Thyroid FNA?
* 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
If person diagnosis with Thy2 colloid nodule, what is the next step?
- Repeat U/S and or FNA
52
If person has a follicular lesion, what is the Thyroid FNA category and how is this managed?
Thy3f , excision
53
What is the thyroid FNA category if malignancy is present? How is this managed?
Thy4/5, excision
54
Classify thyroid neoplasms
Benign follicular adenoma others like lipoma ``` Malignant Papillary carcinoma (80%) Follicular carcinoma (10%) Medullary carcinoma(<5%) Anaplastic carcinoma (1-2%) ``` mets, lymphoma
55
Features of follicular adenomas
* 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
What are the other variants of follicular adenoma?
Hurthlecell adenoma and atyical adenoma
57
Malignant thyroid tumours occur more in male or females ?
Females
58
What predisposes one to malignant thyroid tumors?
genetic(men syndrome) radiation exposure adenoma hashimotos
59
What is the prognosis for papillary ca
good; 98% 5 year survival
60
What is the age range that papillary ca occur in?
20-40 females
61
Describe the pathology aw papillary ca
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
Any invasion occurs in papillary carcinoma?
Propensity for invading lymphatics | regional lymph node mets
63
List the variants of papillary carcinoma
``` •Follicular variant •Oncocytic variant •Columnar variant •Diffuse sclerosing variant •Tall cell variant •Papillary microcarcinoma <1cm Common Incidental finding ```
64
Treatment for papillary carcinoma?
``` total thyroidectomy >1cm lobectomy <1cm and Lateral Neck/ central neck dissection radioactive iodine ablation lifelong eltroxin ```
65
When and why is L thyroxine given?
post operation to suppress TSH
66
What age does follicular carcinoma usually occur?
50-60 females
67
Features of follicular carcinoma
slowly enlarging painless thyroid nodule | micro: capsular,vascular invasion
68
Does spread occur w follicular carcinoma?
haematogenous spread- bone marrow
69
Prognosis of follicular carcinoma
dependent on degree of invasion minimally invasive- 95% survival widely invasive- 30-70% 5 yr survival
70
Treatment for follicular car
``` total thyroidectomy >1cm + radioactive iodine abalation total lobectomy (w/o mets) thyroid hormone (Eltroxin) after surgery ```
71
Define medullary car
Neuroendocrine neoplasm of parafollicular Ccells which secrete calcitonin slow growing
72
What age group does medullary car occur in?
50-60 years
73
What is the % a/w genetic factors in medullary car
20-25% familial / MEN 2
74
When does anaplastic carcinoma occasionally happen?
elderly females
75
How does anaplastic car present?
aggressive and rapid growth - pressure symptoms (oesophagus and trachea) - laryngeal nerve paralysis
76
Any mets occur in anaplastic car?
LN, lungs, bone
77
Differential diagnosis for anaplastic car
Rieldel's thyroiditis due to macro appearance being hard and gritty
78
Micro appearance of anaplastic car
undifferentiated giant cells
79
What is the prognosis for anaplastic car
poor prognosis; usually fatal within 1 year | chemo and radio not effective ; complete resection not possible
80
What are the complications of thyroid surgery?
Hypo-parathyroidism Recurrent Laryngeal Nerve Damage Haemorrhage / Haematoma Infection Recurrence Thyroid Storm
81
Describe thyroid lymphoma
Uncommon Associated with Hashimoto’s thyroiditis Occurs commonly in the 5th decade of life Very responsive to chemo-radiation
82
When is surgery for hyperthyroidism indicated?
Patient choice When Radioactive iodine c/i obstructive/diffuse goitre single toxic adenoma
83
What are the advantages and disadvantages of RAI?
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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