3. Robbins: Thyroid Flashcards
1
Q
Describe the morphology of the thyroid
A
2
Q
What is the mechanism of T3/T4 release from the thyroid?
A
3
Q
Where is thyroglobulin made and stored?
A
Colloid
4
Q
What is thyroglobulin converted into?
A
T4 (thyroxine) and lesser amounts, into T3 (triidothyronine).
5
Q
A
6
Q
Which thyroid hormones binds to [thyroid hormone nuclear receptors] in target cells with greater affinity and have greater activity?
A
T3
7
Q
Actions of thyroid hormone
A
- Increase in the basal metabolic rate (MAIN)
- Carb/lipid catabolism
- Protein synthesis
8
Q
_________ = chemicals that inhibit the function of the thyroid gland
A
Goitrogens: [↓ T3/T4 —> ↑ TSH —> enlargement of the thyroid].
9
Q
What is the MOA of the antithyroid agent, propylthiouracil?
A
Decreases TH production
- Inhibits the oxidation of iodide by TPO => thus, blocks production of TH
- Inhibits the peripheral conversion/deiodination of T4 => T3
10
Q
What occurs when large doses of iodide are given?
A
- Acts as a goitrogen: Blocks release of thyroid hormones by inhibiting the proteolysis of thyroglobulin.
- Thyroid hormone is made and incorperated into colloid, but not released into blood.
11
Q
Hyperthyroidism is also called _______.
A
Thyrotoxicosis
12
Q
Hyperthyroidism/Thyrotoxicosis
- What is it?
- Types and MCC
A
- Hypermetabolic state d/t increase levels of free T3/4
- Primary hyperparathyroidism (MC) and secondary hyperparathyroidism.
13
Q
Types of Primary Hyperparathyroidism
Which is the MC?
A
- Diffuse hyperplasia (Graves disease) of thyroid => MC
- Hyperfunctioning mulinodular goiter
- Hyperfunctioning thyroid adenoma
14
Q
Types of Secondary Hyperparathyroidism
A
- Pituitary thyrotroph adenoma
15
Q
How does the clinical presentation of hyperthyroidism vary?
A
Symptoms exist on a continuum
- 1. Apathetic hyperthyroidism
- 2. Regular hyperthyroidism
- 3. Thyroid storm
16
Q
Symptoms of Regular Hyperthyroidism
A
-
Hypermetabolic state due to too much T3/T4 and overactive sympathetic NS
- Increase in BMR => perspiration, flushing and heat intolerance
- Cardiac manifestations: tachycardia, palpitatio, sinus tachycardia (NL rhythm, but increase rate: a-fib)
- Exophthalmos
- Overative sympathetic NS: nervousness, excited, restless, insomnia, emotionally unstable
17
Q
Thyroid Storm
What is it?
Symptoms
If left untreated what is a common cause of death?
A
Thyroid storm = abrupt onset of SEVERE hyperthyroidism that occurs MC in patients with Graves disease and most likely due to acute elevation of catecholamines
- Febrile
- Cardiac manifestation: tachycardia and CHF
- GI symptoms: diarrhea and jaundic
- Death: due to cardiac arrhythmia
18
Q
Who is more likely to get thyroid storm?
A
- Ppl with Graves disease who are/have
- Pregnancy/postpartum
- Hemithyroidectomy
- Take amiodarone
19
Q
Apathetic hyperthyroidism
What is it?
A
- Thyrotoxicosis that occurs in older adults who have co-morbidities that mask symptoms. Present with
- Unexplained WL
- Worsening CV disease
20
Q
T3/T4 & TSH levels
Primary and secondary hyperthyroidism
A
- Primary: ↑ T3/T4 and ↓ TSH levels
- Secondary: ↑ T3/T4 and ↑ TSH levels
21
Q
TRH stimulation test
- NL rise in TSH =______
A
excludes secondary hyperthyroidism
22
Q
Once a diagnosis of thyrotoxicosis is made, how can we determine etiology?
A
- Measure radioative iodine uptake by thyroid gland
- ↑ uptake by whole gland = Graves
- ↑ uptake by 1 nodule = Toxic adenoma
- ↓ uptake = thyroiditis
23
Q
Treatment of Hyperthyroidism
A
- Treat manifestations with B-blocksrs or NSAIDS
-
Treat underlying disease with:
- High doses of iodide (Wolf-Chaikoff effect)
- Thionamide
- Radiodine ablation
- Surgery
24
Q
MC etiology of Hyperthyroidism
A
Graves disease
25
What is **Graves Disease?**
AI disorder caused by (+) of thyroid epithelial cells by TSI (thyroid stimulating immunoglobulins) autoAb to the TSH-receptor that mimic TSHs action.
26
**_Graves Disease_**
* Triad of symptoms
1. **Hyperthyroidism with gland enlargment**
2. Infiltrative **ophthalmopathy** --\> exophthalmos
3. **Pretibial myxedema/dermopathy =** scaly/indurated skin on shins
27
**_Graves Disease_**
1. MC in:
2. Most common antibody subtype
3. HLA subtypes associated with Graves disease:
4. Lab findings
1. **W 20-40 YO**
2. Thyroid stimulating immunoglobulin (**TSI**)
3. HLA-**DR3** and **B8**
4. **↑ free T3/4; ↓ TSH; ↑ uptake of radioactive iodine** (bc thyroid follicles are STILL being stimulated by TSI)
28
The **exopthalmos** associated with **Graves Disease** is caused by what underlying process?
1. CD4-helper T cells infiltration of retroorbital space and release TSI =\>
2. TSI Ab bind to TSH-receptor on fibroblasts =\> proliferate
3. EOM begin to swell due to edema + inflammation
4. Accumulation of EC matrix components (GAG and chondroitin sulfate)
5. ↑ number and expansion of adipocytes
6. Eyeball pushes forward.
29
The **exopthalmos** associated w/ **Graves disease** appears to stem from activation of which cells in the orbit and via which receptor?
**Orbital preadipocyte fibroblasts,** which have **TSH receptors**
30
**Gross morphology** of Graves Disease
1. **Soft, symmetrical** **enlargement** of thyroid due to diffuse hypertrophy and hyperplasia of follicular epithelial cells
31
Histology of the thyroid in untreated **Graves Disease**
1. Follicular epithelial cells are **taller** and **more crowded** --\> formation of **small papillae WITHOUT fibrovascular cores** that project into the lumen and encroach on the colloid
2. **Colloid** has scalloped margins with **resorption droplets** (colloid in endocytotic vesicles made by pseudopodial extensions of cytoplasm at the lumen)
3. Lymphiod infiltrates + germinal centers
32
How do the papillae seen in graves disease **differ** histologically from those of papillary carcinoma?
**Lack fibrovascular cores**
33
**Hypothyroidism**
* MC in whom?
* Due to?
* Increases with age; W
* **Primary hypothyroidism** \*\*\* vs. **Secondary hypothyroidism**
34
**Primary** ****_hypo_**thyroidism** can be \_\_\_\_\_\_\_, \_\_\_\_\_\_\_, \_\_\_\_\_
**Congenital** vs **Autoimmune** vs **Iatrogenic**
35
**Congenital hypothyroidism** is most often due to \_\_\_\_\_\_\_\_\_
**Endemic iodine deficiency** in the diet during pregnancy.
36
**Inborn errors of thyroid metabolism** causing congenital hypothyroidism is known as what?
Dyshormonogenetic goiter: where one of multiple steps leading to thyroid hormone synthesis is defective:
1. Iodide transport into thyrocyte
2. Organification of iodine (binding of iodine to tyrosine resides of the storage protein, thyroglobulin)
3. Iodotyrosine coupling to form active T3/4
37
Other causes of **hypothyroidism**
1. **Thyroid agenesis** (complete absence of thyroid parenchyma)
2. **Thyroid hyopplasia** (gland is reduced in size)
38
C**retinism**
* **What is it?**
* **Sx**
* Possible causes
**Congenital hypothyroidism t**hat develops in **infancy** or **early childhood**
_Symptoms_:
1. Mental retardation
2. Short stature
3. Coarse facial features and a protruding tongue
4. Umbilical hernia
_Possible causes:_
1. Areas w/o iodine supplementation
2. Result of genetic alterations in normal thyroid metabolic pathways i.e., dyshormonogenetic goiter
39
**_Myxedema_**
* What is it
* Symptoms
* Possible causes
* **_Hypo_**thyroidism that occurs in **older child/adult**
* Symptoms:
1. Mental and physical slowing (sluggish)
2. Weight gain
3. Cold intolerance
4. Decrease cardiac output and hypercholesterolemia
5. Facial edema and yellow skin
40
Histologically, there is an **accumulation** of what in **Myxedema**; leads to what clinical findings?
**- Matrix substances,** such as glycosaminoglycans and hyaluronic acid in skin, subcutaneous tissue, and some visceral sites
- Leads to **nonpitting edema**, **broad/coarse facial features,** **enlarged tongue**, and **deepening** of the **voice**
41
What is the most common cause of **hypo**thyroidism in **iodine**-**sufficient** areas of the world?
**Autoimmune hypothyroidism** i.e., Hashimoto thyroiditis
42
What will levels of TSH be like in pt with **primary hypothyroidism** and **primary hyperthyroidism?**
- Primary **hypo**thyroidism = **↑↑↑ TSH**
- Primary **hyper**thyroidism = **↓↓↓ TSH**
43
Polymorphisms in which immune-regulation associated genes are implicated in H**ashimoto Thyroiditis?**
**CTLA4 and PTPN22**
44
What I**g4-related diseases** is someone with **Reidals thyroididtis** more likely to get?
* 1. **AI pancreatitis**
* 2. **Sclerosing mediastinitis**
* 3. **Idiopathic retroperitoneal fibrosis**
45
**_Goiters_**
* **Goiters** (enlargement of the thyroid gland) is caused by \_\_\_\_\_\_\_\_\_.
* Most often _hypo/hyperthyroidism/euthyroid_
* Degree of enlargement = _\_\_\_\_\_\_\_\_\_\_\__
* **Impaired synthesis of thyroid hormone,** which is most often due to dietary iodine deficiency =\> rise in TSH levels =\> hypertrophy and hyperplasia of follicular cells.
* **Euthyroid**: increase in mass overcomes hormone deficiency. If enlargement is not enough =\> goitrous hypothyroidism.
* Level and duration of hormone deficiency
46
**Diffuse nontoxic (simple) goiter** causes enlargement of the entire gland **without** producing \_\_\_\_\_\_.
**Nodularity**
47
**Causes** of _Diffuse Nontoxic Goiter_
1. ***Endemic*** due to _iodine deficiency_ or _goitrogens_
1. Cassava root/thiocyanate or brassicaceae veggies (broccoli, caulifloer, cabbage and radish)
2. ***Sporadic***, with _unknown etiology,_ but more common in females
48
The **clinical manifestations** of _diffuse nontoxic (simple) goiters_ are most often due to what?
**Mass effect** bc most pt's are clinically _euthyroid_ (normal T3 and T4; TSH is high or upper range of NL):
* 1. Dysphagia
* 2. Hoarseness
* 3. Stridor
* 4. SVC syndrome (flushed face)
49
What are the 2 phases identified in the evolution of **diffuse nontoxic goiter?**
1. **Hyperplastic phase:** Thyroid is diffusely and symetrically mildly enlarged
1. Follicular epithelium can crowd and form _papillary projections._
2. **Colloid involution:** occurs when dietary iodine increases or demand of thyroid hormone increases =\> stimulated follicular epithelium involtes to form a large colloid goiter.
50
Virtually all long-standing simple goiters **convert** into what?
**Multinodular goiters** via recurrent episodes of hyperplasia and involution.
51
Which type of goiter produces the **most extreme enlargements** and are more frequently **mistaken for neoplasms** than any other thyroid disease?
**Multinodular goiters**
52
What morphological feature is missing from **multinodular goiters** which is distinct from **follicular neoplasms?**
There is **_NOT_** a prominent capsule between hyperplastic nodule and compressed thyroid parenchyma.
53
**Older lesions** of multinodular goiter show what histological change?
Areas of **hemorrhage, fibrosis, calcification,** and **cystic** change
54
Morphology of Multinodular Goiters
* **Multilobulated** and **assymetrically** enlarged.
* Cut: nodules have **brown, gelatinous colloid.**
* Older masses: **hemorrage**, **fibrosis**, **calcifcation** and **cystic** changes.
55
Microscopy of **Multinodular Goiters**
1. Colloid-rich follicles lined with flat, inactive epithelium
2. Follicular hyperplasia with degenerative changes due to stress.
56
When an autonomous nodule develops within a long-standing multinodular goiter and produced **hyperthyroidism** this is known as what?
**Toxic** multinodular goiter (aka **Plummer syndrome)**
57
**Clincal presentation** of Multinodular Goiter
Indicence of malignancy
* **Euthyroid** or **subclinical hyperthyroidism (low TSH**), so present with **mass effect** (same sx as diffuse)
* **Low, but not 0,** malignant potential.
58
What are the levels of **T3/** **T4** + **TSH** like in **older pt (\>55 y/o)** with **multinodular goiter?**
**- ↑ T3 and T4**
**- ↓ TSH**
59
What is the purpose of **radioisotope scanning?**
* Determines whether a specific nodule is **hyperfunctioning**. If so, excise or ablate.
* **Low serum TSH** =\> perform a radioactive scan (determines if nodule is hot or cold)
* Hot ---\> I or surgery
* Cold ---\> US and FNA to confirm
* **NL/High serum TSH** =\> perform a US
60
Which type of nodule is more likely to be **neoplastic** (cold or hot)?
Overall, hot and cold nodules are **benign**.
However, **cold nodules** have a BETTER chance at being **malignant**.
61
\_\_\_\_ can be used to determine cellular constituents of a nodule.
**FNA**
62
**Benign** neoplasms of the Thyroid
1. Hyperplastic (adenomatoid) nodules
2. Follicular adenomas
63
**_Solitary Thyroid Nodule_**
* What is it?
* MC in?
* Majority are:
* **Palpable discrete swelling** in a NL thyroid gland
* **W**; incidence **increases with age.**
* **Localized non-neoplastic lesions** (dominant nodule in a multinodular goiter, simple cyst or foci of thyroiditis) or **benign neoplasm** (follicular adenoma)
64
Nodules are more likely to be **neoplastic** if:
* **Solitary** nodules (not multiple)
* Pt is **younger**
* **Males**
65
Nodules are more likely to be **malignant** if:
1. **Hx of radiation to head and neck**
2. Functional nodule that **take up** radioactive iodine (hot nodules) = more likely to be benign
66
What is the **BEST** way to tell the nature of a nodule?
Look at morphology by **FNA** and **surgical resection.**
67
**_Follicular Adenomas_**
* What are they?
* Nonfunctional or functional?
* Clonal proliferation of follicular epithelium that forms a BENIGN _discrete_, _encapsulated_, _solitary masses_ with "thyroid autonomy".
* **Majority are non-functional,** but some can be functional and make thyroid hormone, causing thyrotoxicosis.
68
**_Follicular Adenomas_**
* Gross morphology
* Microscopic morphology
* **Gross**
* Solitary, well-defined, ***_encapsulated_*** mass that ranges in color from [grey-white =\> red-brown].
* _Hemorrage, fibrosis, calcification and cysts_ are common.
* **Microscopic**
1. _Proliferation of uniformly looking follicles + colloid_ (easily ID'd from nearby non-neoplastic thyroid)
2. _Hurthle cells metaplasia/oxyphil:_ cytoplasm of neoplastic cells become eosinophilic
69
Differentiate **[follicular adenomas]** from **[follicular carcinomas]?**
**Intact, well-formed capsule** surrounds the tumor, so it _does NOT invade._
70
What mutations are found in **[toxic adenomas]** and **[toxic multinodular goiters],** but RARE in follicular carcinomas?
Somatic mutations in TSH-receptor signaling pathway: **GOF** of **TSH-R** or a-subunit of Gs (**GNAS**)
=\> **hyperthyroidism** and produces a functional **"hot" nodule** on imaging.
71
Evaluation of ________ is CRITICAL to distinguish **follicular adenoma** from **follicular carcinoma?**
**Integrity of the capsule**
72
**Clinical presentation** of _follicular adenomas_
* Present as a [unilateral, painless mass] discovered during PE. If large =\> problem swallowing.
* If non-functioning = take up less radioactive iodine than NL parenchyma and look like "cold nodules".
73
How is **definitive diagnosis** of adenomas made?
**Remove surgically** =\> **look at integrity of capsule** so that follicular adenoma can be differentiated from follicular cancer.
74
**_Thyroid Cancer_**
* MC in:
* Most thyroid cancers are derived from ________ epithelium and of these, the majority are \_\_\_\_-differentiated.
* **W**: **early --\> middle** adult years
* **Follicular** epithelium (except medullary carcinoma); **well-differentiated**
75
Types of **Thyroid Cancer** and which is the most common?
* **1. Papillary cancer (\>85%)\***
* **2. Follicular cancer**
* **3. Anaplastic undifferentiated cancer**
* **4. Medullary cancer**
76
In the **3 cancers** that are derived from the **follicular epithelium**, genetic mutations are present in what pathways?
**GOF mutations** in the **growth-factor receptor** signaling pathway.
77
The **diffuse slcerosing variant** of **papillary carcinoma** is often associated with a **prominent lymphocytic infiltrate,** simulating what other disease of the thyroid?
**Hashimoto thyroiditis**
78
What are the 2 characteristics of **follicular carcinoma**?
1. **Angioinvasion** =\> spreads hematogenously
2. **Invasion of capsule** =\> forming a mushroom.
79
How is the distinction between **follicular adenomas** and **minimally invasive follicular carcinomas made?**
**Invasion of capsule** and **vascular invasion**
80
Serum levels of what are used for monitoring **follicular carcinoma** recurrence?
**Serum thyroglobulin;** as should be barely detectable
81
Which cancer is recognized based on nuclear features (ground-glass nuclei and pseudoinclusions)
**Papillary carcinomas of thyroid**
82
High aggressive, uniformly lethal cancers
**Anaplastic cancers**
83
Cancers that arise from parafollicular C cells occur sporadically (70%) or famial (30%)
**Medullary cancers**
84
Features of **familial** medullary cancers
**1. Multicentricity**
**2. C-cell hyperplasia**
85
What is Reidels Thyroiditis?
Chronic inflammation (lymphocytes + IgG4 plasma cells) that causes extensive fibrosis of the thyroid gland (**euthyroid**), which can extend to nearby structures (parathyroid gland, recurrent laryngeal nerve and trachea)
=\> produces a "rock hard" thyroid w involvement of adjacent structures in a younger patient that can be confused wiht anaplastic carcinoma.
86
**Young W** has rock hard thyroid with hoarness, hypoparathyroidism and difficulty breathing. What does she have?
**Reidal thyroiditis**
87
**70-80YO W** has rock hard thyroid with hoarness, hypoparathyroidism and difficulty breathing. What does she have?
**Anaplastic carcinoma:** can be hard and extend beyond thyroid
88
What HLA is assx with Hashimoto thyroiditis?
DR5
89
What is **DeQuarvians Thyroiditis?**
**Painful goiter** followed by a period of [transient hyperthyroidism] that lasts for 2-6 weeks; returning back to NL fx in 6- 8 weeks after a URI/virus causes **granulmatous inflammation**. (NO HYPO),
90
What is **Subacute lymphocytic/painless thyroitidits?**
AI-destruction by antiTPOab that causes lymphocytic infiltrate (lympho, plasma cells + germinal centers) of the thyroid gland, commnly **afte rpregnany =\>** tramsient mild hyperthyroidim =\> 1/3 get permant hypothyroidism =\> painless goiter (no hurthlr crll metaplasia or firbosis.
- thyroid is enlarged. but looks NL
