Thyroid Disorders Flashcards
1
Q
Thyroid glands store its secretory substances in the lumen of
A
Follicles
2
Q
The follicular cells are made up of what type of epithelium?
A
Cuboidal to low columnar epithelium
3
Q
Follicular cells surround a central
A
Colloid filled lumen
4
Q
Parafollicular cells are also known as
A
Clear cells or C cells
5
Q
Where are the parafollicular cells located and do they contact the colloid?
A
Periphery and No
6
Q
T4 and T3 are stored where? and to which molecule are they attached?
A
In the colloid
Thyroglobulin
7
Q
Calcitonin opposes what other hormone?
A
PTH
8
Q
Parafollicular cells secrete
A
Calcitonin
9
Q
What symporter actively transports iodide into the thyrocyte?
A
sodium-iodide symporter
10
Q
Within the thyrocyte iodide is rapidly oxidezed by what molecule? with the help of which enzyme?
A
H2O2 /thyroid peroxidase
11
Q
The oxidized iodide is added to which residues in thyroglobulin?
A
tyrosyl residues
12
Q
Which enzyme catalyzes the coupling of the monoidotyrosine and diiodotyrosine to generate T4 and T3?
A
thyroid peroxidase
13
Q
TRH is secreted by?
A
Hypothalamus
14
Q
What is primary hypothyroidism?
A
Hormone deficiency secondary to an intrinsic thyroid gland dysfunction
15
Q
What is secondary hypothyroidism?
A
An inadequate stimulation by TSH results in a deficient thyroid gland function
16
Q
Sexondary hypothyroidism can also be due to
A
Inadequate TRH
17
Q
Thyroid agenesis/hypoplasia is associated with what germline mutations?
A
FOXE1, PAX8, and THRB
18
Q
Can hypothyroidism be the result of drugs?
A
Yes
19
Q
A mutation in which gene increases the risk for follocular carcinoma?
A
PAX8
20
Q
How can the neck present in someone with hypothyroidism?
A
Thyroid gland may be normal in size, diffusely enlarged or atrophic, may be soft and smooth with a lobular texture, or firm and irregular with a variegated nodular texture
21
Q
What is overt primary hypothyroidism?
A
Elevated TSH level >10 mIU/L plus free T4 level below the lower limit of the reference range
22
Q
What is subclinical hypothyroidism?
A
Free T4 level remains the low normal to normal range while the TSH is high
23
Q
What is the most common cause of primary hypothyroidism in developed countries?
A
Hashimotos thyroiditis
24
Q
Hashimotos thyroiditis may occur in association with
A
Autoimmune polyendrocrine syndrome (APS) types 1 and 2
25
What are other types of thyroiditis?
Granulomatous (de quervain) thyroiditis and subacute lymphocytic thyroiditis
26
Hashimotos thyroiditis is more prevalent in which gender?
Women
27
Hashimotos thyroiditis is characterized by circulating autoantibodies against?
Thyroglobulin and thyroid peroxidase
28
During Hashimotos thyrotoxicosis how are the levels of T3, T4 and TSH?
TSH is decreased, T3 and T4 is increased and also radioactive iodine uptake is decreased
29
In Hashimotos thyroiditis, painless enlargment of the gland may precede what?
Systemic manifestations
30
Enlargment of the gland of someone with Hashimotos thyroiditis is...
Symmetric and diffuse
31
In Hashimotos thyroiditis, the thyroid gland eventually...
Atrophies
32
What other labs should be done in a person with Hashimotos thyroiditis aside from TSH/T4 and T3?
Antithyroid peroxidase antibody, antithyroglobulin antibody and also an ultrasound
***Diffuse heterogeneity on ultrasound suggests autoimmune thyroiditis***
33
In Hashimotos thyroiditis, epithelial cells undergo ?
Hurthle cell change
34
Subacute lymphocytic thyroiditis and postpartum thyroiditis are variants of?
Autoimmune thyroiditis
35
In subacute lymphocytic thyroiditis as well as postpartum thyroiditis, how do patients intially present?
Mild hyperthyroidism, goitrous enlargment of the gland or both
36
In subacute thyroiditid and postpartum patients tend to transition from hyperthyroidism to
Hypothyroidism before recovery
37
What is a key difference between hashimotos thyroiditis and subacute lymphocytic and postpartum thyroiditis?
In subacute lymphocytic thyroiditis as well as postpartum thyroiditis, there is a lack of fibrosis and Hurthle cell metaplasia is not prominent
38
What triggers subacute granulomatous thyroiditis?
Viral infection
39
Subacute granulomatous thyroiditis is also called...
De Quervain thyroiditis
40
In subacute granulomatous thyroiditis there is painful what?
Enlargment of the thyroid gland
41
For how long does the transient hyperthyroidism state lasts in granulomatous thyroiditis?
2-6 weeks
42
How do the T4, T3 and TSH look like during the hyperthyroid state of someone with granulomatous thyroiditis?
High T4 and T3, low TSH and decreased radioactive iodine uptake
43
How does thr gland of someone with subacute granulomatous thyroiditis look like?
Unilateral or bilateral glandular growth
| Firm consistency and intact capsule with capability of adhering to adjacent structures
44
What can be found microscopically in the early and late phases of inflammatory phase of subacute granulomatous thyroiditis?
Neutrophils forming microabscesses -early phase
Later phase- aggregates of lymphocytes, activated macrophages, and plasma cells associated with collapsed and damaged thyroid follicles
Multinucleated giant cells surround fragments of colloid
Chronic inflammatory infiltrate and fibrosis may replace the foci of injury
45
What are some causes of primary hyperthyroidism?
1. Grave’s disease
2. Hyper-functional toxic multinodular goiter
3. Hyperfunctional toxic adenoma
46
What are some causes of secondary hyperthyroidism?
1. TSH-secreting pituitary adenoma
| 2. Ingestion of exogenous thyroid hormone
47
What are some examples of ophthalmopathy in Grave’s disease?
Eye lid retraction, perioribital edema, episcleral vascular injection, conjunctival swelling (chemosis), proptosis (exopthalmos)
48
What is pretibial myxedema?
A condition that is precipitated by the deposition of glycosaminoglycans in the dermis of the skin
49
How do patients with pretibial myxedema present?
Midly pruritic, orange peel-like thickening of the skin along the anterior aspeft of the shins
50
A low TSh and increased free T4 is indicated of?
Thyrotoxicosis
51
A decreased TSH and a normal free T4 is indicative of what conditions?
T3 thyrotoxicosis
Mild or subclinical thyrotoxicosis
Nonthyroidal illness
52
A normal to increased TSH and an increased free T4 is indicative of what?
TSH-secreting pituitary adenoma
Thyroid hormone resistance syndrome
Familial dysalbuminemic hyperthyroxinemia
53
What important diagnosis is made in Grave’s disease?
Fractional 24-hour radioiodine uptake which is going to fire up.
Also, a thyroid ultrasonography can confirm the presence of solitary or multiple thyroid nodules
54
How is the morohology of the thyroid of someone who has Grave’s disease?
Enlargment of the thyroid is usually symmetrical. This is secondary to diffuse hypertrophy and hyperplasia of thyroid follicular epithelial cells
55
How does the microscopic morphology look like in someone who has Grave’s disease?
Tall crowded follicular cells which may result in the formation of small papillae (without fibrovascular cores)
-pale colloid centers
Presence of small, clear vacoules on the edge of the colloid
56
Colloid goiter is also known as
Diffuse non toxic sinple goiter
57
Colloid goiter is distributed in an
Endemic and sporadic fashion
58
Most patients that present these nontoxic goiters are
Eurhyroid
| -The TSH, T3 and T4 levels tend to be in a normla range
59
Most symptoms of someone who has a colloid goiter tend to come from?
The mass effect of the goiter
60
Endemic goiter is associated with
Endemic iodine deficiency
61
The deficiency of iodine in endemic goiter leads to
A decreased synthesis of thyroid hormones which leads to an increase in TSH
62
Patients with endemic goiter develop what?
Follicular cell hypertrophy and hyperplasia and goitrous enlargment
63
How will the thyroid follicules of someone with goiter look like?
Thyroid follicles are lined with inactive, flattened epithelial cells and filled with abundant stored colloid
64
What is toxic multinodular goiter?
Characterized by the presence of multiple autonomously functioning thyroid nodules
65
The nodules in a person with toxic multinodular goiter are capable of?
Synthesizing and secreting excessive amounts of thyroid hormone
66
Toxic multinodular goiter is more common amongst the
Older population
67
The enlargment of the thyroid gland of someone who has multinodular goiter is?
Assymetric although both lobes are enlarged
68
Most patients with multinodular goiter are
Eurhyroid
69
What does “hot nodules” mean?
Increased activity on radionuclide scintigraphic scanning
70
Functional nodules have a
Less risk of malignancy than cold nodules
71
If there is a personal history of neck irradiation in childhood this increases the risk for
Malignancy of thyroid nodules
72
Medullary thyroid cancer is familial in
50% of cases
73
Medullary thyroid cancer are associated with
Multiple endocrine neoplasia type 2 (MEN 2)
74
Papillary thyroid cancers are familial in
10% of cases
75
A well perfomed physical examination of thyroid nodules should define
Size, consistency, surface texture, mobility and tenderness
76
Malignancy of thyroid nodules of suggested by
Fixation and ipsilater regional adenopathy or vocal cord paresis
77
Multinodularity of the thyroid gland may reflect a
Benign process
78
A toxic adenoma will have a
Decreased level of TSH which means it is benign and autonomoulsy functioning
79
What is the most accurate test to exclude or confirm malignant disease in patients with a nodule and a normal TSH level?
Fine needle biopsy
80
Ultrasonographic guidance and on-site preliminary cytologic assesment can improve the yield of biopsy when it comes to
Thyroid nodules
81
Thyroid adenomas in most cases are
Discrete, solitary masses derived from follicular epithelium
82
In most cases thyroid adenomad are kot precursors to
Carcinomas
83
Modt thyroid adenomas are
Non functional meaning that they do not secrete T3 and T4 independantly from TSH
84
Toxic adenomas are due to
Gain of function mutations of the TSH receptor signaling
TSHR and GNAS mutations
85
R
86
How do the adenomas look macroscopically?
Solitary, spherical, encapsulated well defined lesion
87
Thyroid adenomas have small
Follicles that are packaged closely
88
What is the hallmark of all follicular adenomas?
Presence of an intact well formed capsule encircling the tumor
89
Thyroid adenomas may undergo
Hurthle change
90
Which thyroid carcinoma is poorly differentiated?
Anaplastic
91
Medullary carcinomas are
Undifferentiated
92
Papillary and follicular carcinomas are
Well differentiated
93
Papillary carcinomas mostly involve a gain of function mutation in which genes?
RET or NTRK1
| BRAF
94
Both mutations (RET or NTRK1 or BRAF) set off a signaling cascade down the
MAPK pathway
95
In papillary carcinomas there is
Either a paracentric inversion of chromosome 10 or a reciprocal translocation between chromosomes 10 and 17
96
The chromosomal rearrnagment in papillary carcinoma activates the
Transcription of the RET tyrosine-kinase domain in follicular cell which triggers signaling along the MAPK pathway and an uncontrolled proliferation
