La thyroïde Flashcards
1
Q
D’où est-ce que le thyroïde provient?
A
Provient de l’entoblaste:
- Bourgeon qui se forme à partir du plancher du pharynx (foramen cecum) et descend antérieurement à la trachée puis bifurque de chaque côté formant les lobes thyroïdes
2
Q
D’où est-ce que les parathyroïdes provient?
A
3e et 4e poches brachiales
3
Q
What is a lingual thyroid?
A
abnormal mass of ectopic thyroid tissue seen in base of tongue caused due to embryological aberrancy in development of thyroid gland
4
Q
What is a thyroglossal cyst?
A
A fibrous cyst that forms from a persistent thyroglossal duct
5
Q
What are some examples of “dysgenèse thyroïdienne”? (5)
A
- Agénésie thyroïdienne (pas de thyroïde)
- Hypogénésie thyroïdienne (not enough hormone production)
- Thyroïde ectopique (wrong place)
- Thyroïde linguale
- Kyste thryéoglosse
6
Q
Anatomy of the thyroid:
A
- Usually 2 lobes but in 30% of patients there is a pyramidal lobe in between the two
- Usually between 15-20g
- Dimensions: 4x2x1 cm
7
Q
Which veins and arteries supply the thyroid?
A
Three veins: superior, medial, inferior
Two arteries: superior, inferior
8
Q
How/why would you observe and palpate the thyroid?
A
- For signs of a: goiter, nodule, or signs of inflammation
- Stand in front or behind the patient to palpate but usually it’s done from the back
- You must also palpate the neck to look for adenopathies
9
Q
How to auscultate the thyroid?
A
Place stethoscope on each lobe of the thyroid to listen for a murmur (souffle)
A murmur = increased vascularization/tubulant circulation
- hyperT4 –> inc. vascularization –> inc. murmur +++
10
Q
What are the two cell types in the thyroid?
A
- Follicular cells (epithelial): form unicellular thyroid follicles
- Secrete:
- Thyroid hormones (T3 and T4)
- Thyroglubin: protein that stocks iodine
- Colloïde: amalgam of thyroglobulin
- Secrete:
- Parafollicular cells/c-cells: found between the follicles
- Secrete
- Calcitonin: regulates levels of calcium and phosphate
- Secrete
11
Q
What are the two thyroid hormones and their precursors?
A
Hormones:
- Thyroxine (T4)
- Triiodothyronine (T3)
Precursors:
- Diiodotyrosine (DIT)
- Monoiodotyrosine (MIT)
12
Q
Thyroid histology:
A
13
Q
What is the difference between T4 and T3?
A
T4:
- Weaker hormone than T3
- 100% comes from thyroid
T3:
- Much stronger than T4
- 85% comes from transformation of T4 –> T3 in the body
- 15% comes from the thyroid
14
Q
What are the 6 steps of thyroid hormone synthesis?
A
- Captation de l’iode
- Organification de l’iode
- Iodination des thyrosines
- Couplage des tyrosines iododées
- Libération du T3 et T4
- Récupération de l’iode (when hormones are used, iodine is recaptured and taken back to the thyroid)
15
Q
What happens if there’s a problem with one of the steps of thyroid hormone synthesis?
A
It will cause hypothyroidism due to dyshormonogenesis thyroidienne
Usually congenital diseases that are dx during childhood
16
Q
What happens to thyroid hormones in periphery?
A
T4 transformed into T3
T4 and T3 are degraded and iodine is put back into circulation either by:
- Repris par less cellules folliculaires de la thyroïde (most)
- Excrété par le rein
17
Q
What is the half-life of T4 and T3?
A
T4 (thyroxine) –> around 7 days
T3 (triiodotyronine) –> 24 hours
18
Q
Where does iodine come from?
A
Not very abundant in nature
- Iodine has been added to salt in most developed countries (in Asia/countries surrounded by water.. iodine can come from ocean)
- Contract products used in radiology
- Certain medications contain iodine (amiodarone)
- PSN: algae (found in a lot of PSNs), kelp, etc.
19
Q
What does a normal thyroid do when there is a deficit/surplus/or sudden surplus in iodine?
A
- Deficit: increased captation
- Surplus: decreased captation
- Sudden surplus: Wolff-Chaikoff effect
20
Q
Wolff-Chaikoff in normal thyroid:
A
Effect that allows your body to avoid forming excess thyroid hormone
Decrease capitation and organification of iodine
Transitory effect (2-4 weeks) and then once things are back to normal, T4 and T3 synthesis starts again
21
Q
What does an abnormal thyroid do when there’s a deficit/surplus/or sudden surplus in iodine?
A
- Deficit: hypoT4
- Surplus: hyperT4
- Sudden surplus: hyperT4/hypoT4 depending on condition
22
Q
How can iodine cause hypoT4?
A
Surplus in iodine –> Wolff-Chaikoff but it’s not transitory (you get stuck) which causes hypoT4
(Thyroïdite d’Hashimoto)
23
Q
How can iodine cause hyperT4?
A
Thyroïde est avide d’iode d’où thryotoxicose
Examples:
- Graves
- Multinodular goiter
- Nodule chaud
- Goiter due to deficit in iodine
24
Q
How are T4 and T3 transported in the body?
A
T4 and T3 are relatively insoluble in water –> bound to transport proteins
- T4: 0.01% libre
- T3: 0.1% libre
25
Which proteins transport thyroid hormones in the body?
Thyroxine-binding globulin (TBG): 70%
Transthyrétine (thyroxine-binding prealbumin): 20%
Albumine: 10%
26
Axe hypothalamo-hypophyso-throïdien = axe thyréotrope
27
How is the axe thyroïdien regulated?
**Very tight regulation**
T3 --\> prodominant role in retroaction
TRH --\> stimulates TRH
28
What is the difference between primary and central thyroid illnesses?
**Primary:** thyroid disease comes from thyroid itself
**Central:** thyroid disease comes from pituitary and hypothalamus
29
When looking for a primary thyroid illness what do different TSH levels indicate?
Normal --\> no dysthyroidia
High --\> primary hypoT4
Elevated --\> hyperT4
30
How are thyroid hormones measured?
Total measurements don't necessarily reflet the metabolic state of someone
**T4 libre (FT4)** --\> not influenced by transport proteins
**T4 totale** --\> influenced by transport proteins
**T3 totale (TT3)** --\> influenced by transport proteins
31
What can modify TBG levels?
Increased by:
* Genetics
* Estrogen
* Hepatitis
Decreased by:
* Genetics
* Androgens
* Cirrhosis
* Nephrotic syndrome
32
When is the TSH measurement not reliable?
in central hypoT4
33
When looking for a central thyroid illness what do different TSH levels indicate?
**Normal** --\> doesn't exclude anything
* TSH normal + increased T4 = central hyperT4
* TSH normal + decreased T4 = central hypoT4
**TSH ABNORMALLY NORMAL**
**Increased** --\> TSH increased with T4 slightly increased = central hyperT4
**Decreased** --\> TSH decreased with T4 decreased = central hypoT4
**ALWAYS LOOK AT TSH FIRST AND THEN LOOK AT T4 AND WHAT IT SHOULD BE**
34
What can a low T4 indicate?
If TSH increased --\> primary hypoT4
If TSH not increased (normal or low) --\> central hypoT4
35
What are the three common antibodies found in hypo/hyperT4?
Anticorps anti-TPO (Hashimoto)
Anticorps anti-Thyroglobuline (cancer)
Anticorps anti-récepteur de la TSH (TSI, TRab --\> Graves, LATS)
36
In which percent of the population are the three kinds of antibodies found?
**Anti-TPO:**
* Normal popuation: 10%
* Hashimotos: 90%
**Anti-thyroglobuline:**
* Normal population: 3%
* Important in cancer follow ups
**TRab:**
* Normal population: 1%
* Graves: 90%
37
What is thyroglobulin hormone measurement useful for?
Cancer différentiés de la thyroïde (si élévée --\> signe de récidive)
Hyperthyroïdie d'origine factice:
* TBG should be increased in all causes of thyrotoxicosis except for factice
38
How does scintigraphie thyroïdienne work?
Usually done over 2 days
1. Day 1: take radioactive tracer
2. Day 2: measurement of capitation and take images of thyroid
39
What is the purpose of a scintigraphie thyroïdienne?
Evaluate function and anatomy of the thyroid
40
Why is scintigraphie thyroïdienne so important? (3)
1. Permet de préciser la cause d'hyperT4
2. Permet de différentier un nodule chaud d'un nodule froid
3. Permet de localiser la thyroïde particulièrement chez l'enfant
41
Important things to know before doing a scintigraphie thyroïdienne?
Counter indicated in pregnant/breastfeeding women and in children (unless trying to locate thyroid)
Antithyroidiens and Synthroid must be stopped before doing a scintigraphie
Beta blockers don't impact scintigraphie
42
What would cause increased iodine capture on a scinti?
Graves
Goitre multinodulaire toxique
Nodule chaud
Tumeur d'hypophyse produisant TSH (hyperT4 centrale)
43
What would cause decreased iodine capture on a scinti?
Thyroidite (silencieuse, post-partum, sub-aigue --\> hypoT4 phase)
Ingestion of thyroid hormone
Antithyroid rx (methimazole, PTU)
Iodine contamination
44
What is a thyroid echo useful for?
Evaluating nodules and cancer followups
45
Why would you do a thyroid echo?
**DO NOT DO IT BECAUSE OF BLOOD TEST RESULTS**
Do if during examen physique you find a node, masse, or abnormal ganglion
46
What is a thyroid TACO useful for?
Determine if there's an obstruction (trachea/oesophagus) by a goiter
Evaluate a sub-sternal goiter (médiastin)
Evaluate recurrence/externsion of néo
47
What do thyroid hormones do in the body?
**Regulate metabolism**
Surplus --\> thyrotoxicosis (hypermetabolism)
Deficit --\> hypoT4 (hypometabolism)
48
What do thyroid hormones do in children?
All the others +
Development/maturation of the brain
Growth and skeletal maturation
49
What are the signs of hyperT4 in children?
Irritability, emotional instability
Hyperactivity
**Decreased academic performance**
Accelerated growth (rare)
Accelerated bone maturation (rare)
**CAN BE CONFUSED WITH ADHD IN SOME CHILDREN**
50
What are the signs of hypoT4 in children?
All the normal ones +
Mental delay (cretinism) if before 3 years old
Delayed growth
Delayed bone maturation
Decreased academic performance
Delayed puberty or early puberty
51
What is the global action of thyroid hormones?
Increase O2 consommation
Increase basal metabolism
Increase heat production
52
What are the normal sx of hyperT4?
Fatigue
Heat intolerance
Hot/sweaty skin
Weight loss even if appetite is increased
Increased Rx metabolism
Hyperthermia (si tempête thyroidienne)
53
What are the normal sx of hypoT4?
Fatigue
Shivers
Cold skin
Weight gain and decreased appetite
Decreased Rx metabolism
Hypothermia (coma myxedémenteux)
54
What is the action of thyroid hormones on proteins, lipids, and glucose?
Proteins:
* increased synthesis and degradation
Lipids:
* Increased cholesterol synthesis and degradation
Glucose:
* Increased hepatic neoglugenisis
* Increased intestinal absorption
* Increased glycogen degradation
55
Hypo and hyperT4 and lipids, protein, and glucose:
Hyper:
* loss of muscle mass/force (proximal myopathy)
* glucose intolerance (can cause db)
* decreased cholesterol levels
Hypo:
* muscular hypertrophy (rare)
* hypoglycemia (coma myxodémateux)
* hypercholesterol
56
What are the effects of hyperT4 on the CV system?
Tachycardia
Increased contraction --\> SYSTOLIC hypertension
Palpitations
57
What are the effects of hypoT4 on the CV system?
Bradycardia
DIASTOLIC hypertension
58
What are the effects of hyperT4 on the SNS?
Shakes
Sweating
Palpitations
Réflexes ostéotendineux vifs
59
What are the effects of hypoT4 on the SNS?
Delayed relaxation phase in osteotendinous reflexes
60
What are the effects of hyperT4 on the respiratory system?
Tachypnée
Weakness of respiratory muscles
61
What are the effects of hypoT4 on the respiratory system?
Hypoventilation --\> hypoxemia/hypercapnia
Weakness of respiratory muscles
62
What are the effects of hyperT4 on the digestive system?
Hyperdefecation --\> diarrhea
63
What are the effects of hypoT4 on the digestive system?
Constipation
64
What are the effects of hyperT4 on the bones?
Osteoporosis
65
What are the effects of hypoT4 on the bones?
Delayed growth and bone maturation in children
66
What are the effects of hyperT4 on the SNC?
Hyperkinesis (muscle spasms)
Emotional liability
Decreased concentration
Depression
67
What are the effects of hypoT4 on the SNC?
Hypokinesis (movements have a “decreased amplitude”)
Decreased/slowed cognitive function
Depression
68
What are the effects of hypoT4 on the muscles?
Muscular hypertrophy (rare)
Hypoventillation
Myalgia
69
What are the effects of hyperT4 on the muscles?
Loss of muscle mass/force of skeletal muscles (proximal myopathy)
Dyspnea
70
What are the effects of hypoT4 on the endocrine system?
Decreased GH
Increased PRL
Menometrorrhagia (prolonged or excessive uterine bleeding occurs irregularly and more frequently than normal)
Anovulation and infertility
Decreased/early puberty
Decreased cortisol clearance
71
What are the effects of hyperT4 on the endocrine system?
Diabetes exacerbation
Oligomenorrhea, amenorrhea (loss/infrequent periods)
Anovulation, infertility, miscarriage
Gynecomastia (increased conversion of testosterone into estrogen)
Increased cortisol clearance
72
What is euthyroidism?
Normal thyroid function that occurs with normal serum levels of TSH and T4
73
What is the difference between hyperthyroidism and thyrotoxicosis?
**Hyperthyroidism** refers to increased thyroid hormone synthesis and secretion from the thyroid gland,
whereas **thyrotoxicosis** is characterized by the clinical manifestations of inappropriately high thyroid hormone action in tissues (increased thyroid hormone presence)
74
What is a goitre?
Thyroid is bigger than usual
Usually provoked by increased thyroid stimulation: TSH, TRabs, other antibodies
75
What is a simple goitre?
No nodes, uniform increased thyroid size
76
What is a multinodular goitre?
Multiples nodes, heterogenous gland
(Zones with hyperplasia, fibrosis, and necrosis)
77
What are the three main kinds of goitres?
1. Toxic: hyperT4
2. Euthyroid (normal T4 and T3)
3. Associated with hypoT4
78
What sx are associated with thyrotoxicosis?
Fatigue
Hyperactivity
Anxiety, nervousness, emotional liability
Heat intolerance/increased sweating
Palpitations
Shaking
Hyperdefication
Oligomenorrhea and amenorrhea
79
What signs are associated with thyrotoxicosis?
Tachycardia, FA
Weight loss
Hyperkesisis
Lid lag (rétard palpébrale)
Hot, sweaty skin
Slight shaking
Proximal muscle weakness, loss of muscle mass
Réflexes ostéotendineux vifs
80
Causes of thyrotoxicosis if scinti capture is high:
Graves
GMN toxique
Adénome toxique (nodule chaud)
Adénome hypophysaire secrétant de la TSH (VERY RARE!)
81
Causes of thyrotoxicosis if scinti capture is low:
**Hormones released cause thyroid was damaged:**
1. Thyroiditis (subacute, postpartum, silent, radiation)
Induced by iodine
Factice
82
What are the possible treatment methods available for thyrotoxicosis?
Depending on cause and sx:
1. Antithyroid synthesis (thionamides)
2. Radioactive iodine (I-131)
3. Thyroidectomy
4. Beta-blockers (tx sx not cause)
83
What are the two available thionamines?
PTU and methimazole (tapazole)
84
PTU vs Tapazole:
PTU:
* Half-life: 75 mins
* Preferred in:
* First trimester
* Tempête thyroïdienne
Tapazole:
* Half-life: 4-6 hours
85
How does PTU work?
Inhibits organification of iodine
Inhibits iodinated tyrosine coupling
**Decreases conversion of T4 into T3**
86
How does tapazole work?
Inhibits organification of iodine
Inhibits iodinated tyrosine coupling
87
What are some side effects of PTU and tapazole?
Éruption cutanée
Liver: PTU --\> hépatite toxique, tapazole --\> cholestase hépatique
Agranulocytosis (acute condition involving a severe and dangerous lowered white blood cell count)
88
How does radioactive iodine work?
Iodine is mainly captured by the thyroid and when radioactive iodine is captured it'll cause destruction of thyroid cells
Side effects:
* Transitory increase in thyroid hormone (due to tissue destruction)
* **Worsening of Graves orbitopathy (GRAVES IS A 100% COUNTER INDICATION)**
* **Permanent hypoT4 in most patients**
89
Specifics on radioactive iodine:
Antithyroid rx must be stopped 5-7 days before to allow thyroid to regain function/start capturing iodine again
Beta-blockers can be continued/given at the same time
**Can only be used in children if in later stages of puberty or if growth is basically done**
90
What are the counter-indications for taking radioactive iodine?
Severe thyrotoxicosis
Ophthamopathie
Pregnancy/breast feeding
Low iodine capture shown on scinti
91
What are the two kinds of thyroidectomies and what the advantage of having one?
Total: graves, GMN
Partial: toxic adenoma in thyroid
Advantages: very quick resolution of thyrotoxicosis
92
What are the risks involved with a thyroidectomy?
Damage to "nerfs récurrents laryngés"
* vocal cord paralysis
* if on both sides: risk of insuff. respiratoire (will need tracheostoma)
Damage to PTHs (can cause permanant/transitory hypoPTH)
HypoT4 if total thyroidectomy
93
Why are beta-blockers used for thyrotoxicosis?
Decrease adrenergic sx
94
What is Graves?
Most common cause of thyrotoxicosis
Autoimmune disorder:
* TRabs stimulate TSH receptors causing overproduction of T4 and T3
More common in W \> M
Genetic predisposition
Can be exacerbated by a sudden surcharge of iodine
95
How does Graves present during investigations?
T4L and T3 increased
TSH decreased
Scinti:
* Increased homogenous iodine capture
96
What are some signs and sx of Graves?
Thyrotoxicosis signs and sx
**AND specific to Graves:**
* Orbitopathy
* Dermopathy
* Neonatal hyperT4 (antibodies pass from mom to fetus)
97
How to treat Graves? (5 ways)
1. Antithyroid rx alone
2. Radioactive iodine (must lower T4 levels first and cannot be done if orbitopathy)
3. Antithyroid + radioactive iodine (get near hypo so iodine can enter)
4. Surgery (rare but most remove whole thyroid.. done when rxn to antithyroid rx and iodine is counterindicated)
5. Beta-blockers to tx sx
98
What is orbitopathie de Graves?
**TRab onto receptors in eyes that are very similar to TSH receptors in thyroid**
Causes swelling of orbital muscles (lymphoid infiltration) which leads to proptosis, conjunctival congestion, periorbital edema, muscular fibrosis (diplopia), compression of optic nerve (can cause vision loss)
99
What is dermopathie de Graves?
Rare: 2-3% of pts
a skin condition characterized by red, swollen skin, usually on the shins and tops of the feet
100
What is a GMN toxique?
Maladie de Plummer
Usually in people \> 50
History of GMN non toxique
Nodules become autonomous and no longer listen to TSH
**HyperT4 can be provoked by a sudden charge in iodine (ex: contrast products and amiodarone)**
101
How does GMN toxique present during investigations?
T4L and T3 increased
TSH decreased
Scinti:
* Heterogenous increased iodine capture (some cells are still normal and listen to TSH)
102
What are some signs and symptoms of GMN toxique?
Normal signs/sx of thyrotoxicosis
BUT
usually takes more time to show sx compared to Graves and the gland is usually heterogenous, asymmetric, and a large volume
103
How to treat GMN toxique?
Same as Graves except no counter-indication for iodine since there's no orbitopathy
Surgery is more common
104
What is a toxic adenoma?
Mutation of TSH receptor (makes it constantly activated) which causes excessive T4/T3 secretion and clonal expansion of cells which will cause a **node (nodule chaud/toxique)**
Same signs/sx as other forms of thyrotoxicosis but with a palpable nodule (sometimes)
105
How does a toxic adenoma present during a scinti?
T4L and T3 increased
TSH decreased
Scinti:
* Localized excessive +++ iodine capture --\> nodule chaud autonome
* Rest of thyroid doesn't capture since TSH is decreased
106
How to tx toxic adenoma?
Antithyroid alone
Radioactive iodine alone (MOST COMMON)
Antithyroid + radioactive iodine
Surgery (quite common)
Beta-blockers (for sx management)
107
Radioactive iodine and toxic adenomas:
Will only destroy the cells in the adenoma (only ones capturing iodine)
Normal cells will later resume once adenoma is destroyed
Slight risk of post-iodine hypoT4 but much lower than in other pathologies
108
What is thyroiditis?
Inflammation of the thyroid
109
What are the 5 most common kinds of thyroiditis?
1. Hashimotos: different than all the other ones (will just cause hypoT4)
2. Subacute
3. Silent
4. Post-partum
5. Radiation
110
What are the three phases of thyroiditis?
ALL FORMS EXCEPT HASHIMOTOS:
1. HyperT4 (thyroid cells destroyed and release T4/T3)
2. HypoT4 (thyroid is damaged... TSH increased but can't do anything)
3. Euthyroid: thyroid heals and returns to normal
111
What is the pathophysiology of thyroiditis?
Destruction (acute) of thyroid by aggressor --\> sudden release of thyroid hormones --\> temporary thyrotoxicosis
Thyroid stops producing and hormones released run out but takes a couple weeks/months for the thyroid to heal --\> hypoT4
112
Investigation during different phases of thyroiditis:
**HyperT4:**
* TSH low
* FT4 and T3 high
* Scinti: VERY low capture (cells too damaged)
**HypoT4:**
* TSH high
* FT4 high and T3 high/normal
**Euthyroid:**
* TSH, FT4, and T3 normal
113
How to treat hyperT4 phase of thyroiditis?
Antithyroid Rx are useless because iodine isn't being captured.. the thyroid is just releasing its stock
Beta-blockers to manage symptoms
114
How to treat hypoT4 phase and euthyroid phase of thyroiditis?
**Euthyroid**: NO TREATMENT
**HypoT4:** no tx if asx but if sx --\> Synthroid
**Recuperation period:**
* Stop Synthroid after 4-6 months
* Follow TSH levels for the following weeks/months
115
What is subacute thyroiditis?
Also called De Quervain or Granulomatous
Usually preceded by IVRS
**Most likely caused by viral infection**
**Unique aspects (during hyperT4 phase)**
* Fever, myalgia, general malaise
* Painful thyroid
* Increased "vitesse de sédimentation"
* Permet de détecter une inflammation ou une infection
* Tx with AINS/anti-inflammatory or prednisone if pain +++
116
What is silent thyroiditis?
Painless thyroiditis
Likely an autoimmune cause (lymphocyte infiltration of thyroid)
HyperT4 and hypoT4 usually quite mild
Normal thyroid size and tx usually unnecessary
117
What is postpartum thyroiditis?
Usually in the 6 months after giving birth
**Probably an autoimmune cause (maybe variant of Hashimotos)**
* **Immune system drops when pregnant --\> after giving birth it spikes back up which can exacerbate autoimmune disorders**
HyperT4 and hypoT4 usually quite mild
Normal thyroid size and tx usually unnecessary
118
What is radiation thyroiditis?
Caused by tx with radioactive iodine
Usually in 4-7 days after taking I-131
119
What is factitious thyroiditis?
Due to excessive T4/T3 **consumption**
Can be done on purpose OR from PSNs that may contain thyroid extracts
Same symptoms of thyrotoxicosis but **NO GOITRE**
Investigation: TSH low, FT4 and T3 high
Scinti: low capture
**IF SUSPECTED TEST TGB BECAUSE WILL BE INCREASED WITH ALL OTHER CAUSES OF THYROIDITIS**
120
What is a thyroid storm?
VERY SEVERE thyrotoxicosis
mortality --\> 20-30%
**Usually due to adjacent undiagnosed thyroid disease exacerbated by infection, chx, or iodine**
121
What are the cardinal sx of a thyroid storm? (4)
Fever \> 38.5
Tachy \> 140 (can even cause pulmonary edema)
N/V, diarrhea
Confusion all the way to coma
122
What are the different causes of hypoT4?
Primary (95%)
Central (5%)
123
Neonatal period of hypoT4:
Thyroid hormones are crucial for the development and growth of the brain especially before the age of 3
If hypoT4 is not treated, it can cause significant mental delays (cretinism)
Usually asx at birth and detected through heel prick test after birth
124
What are the symptoms of hypoT4 in babies/toddlers?
Hypotonia
Difficulty latching and suckling
Lethargia
125
What are the symptoms of prepubescent hypoT4?
Delayed growth (after 2)
Delayed/early period
126
What are the classic sx of hypoT4?
Fatigue
Slowed cognitive function, and movement
Chills
Weight gain (\< 10% pre hypoT4 weight)
Constipation
Myalgia
Menometrorragia
Dry skin and hair loss
127
What are the classic signs of hypoT4?
Bradycardia, pericardial effusion, **DIASTOLIC** hypertension
Slowed reflexes (slowed relaxation phase)
Cold/dry skin
Oedème (sans godet)
Periorbital edema
Goitre often present
128
What are the neonatal signs of hypoT4?
Jaundice +++
Macroglossia (unusually large tongue)
Abnormally large anterior fontanel
Umbilical hernia
129
What are some other consequences of hypoT4?
Dlpd
Anemia
AST/ALT increase
Increased CK
130
How does hypoT4 present during investigation?
TSH high
T4 low
T3 normal --\> low
* Normal at the start but will drop as hypoT4 progresses
Anti-TPO often + (most often in Hashimoto)
Imagery useless unless you're trying to find a dysgenesis in a baby/child --\> in this case use scinti
131
What can cause a primary hypoT4?
Thyroiditis:
* Hashimoto --\> most frequent
* Other ones --\> hypoT4 phase
Destruction of thyroid:
* Thyroidectomy
* Iodine-131
* External radiation
Medication:
* Antithyroid
* Lithium --\> decrease synthesis and release of already formed
* Amiodarone
* Cancer medication: check point inhibitors and tyrosine kinase inhibitors
Diet:
* Diète goitrogène ou déficit en iode
132
Which congenital abnormalities can cause primary hypoT4?
Dysgènese: lungual, ectopic, anégésie
Dyshormogénèse: enzymatic deficit (usually goitre)
133
What can cause a central hypoT4? and what will investigations show?
Pituitary or hypothalamic disorders
Investigations:
* TSH normal or low --\> useless
* FT4 low
* TT3 normal to low
134
What are the signs and sx of a central hypoT4?
Sx: classic symptoms along with other potential hormonal deficits
## Footnote
**Signs: NO GOITRE**
135
How to treat central hypoT4?
Treat cause not just sx
**IF CORTISOL DEFICIT AS WELL**
* **Always treat hypocortisolism first before hypoT4**
* **Giving thyroid hormones first will increase metabolism nd further decrease cortisol levels and can send pt in to Addisonian choc**
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What will happen to your thyroid tests if you take biotin?
Excess biotin will perturb TSH and T4 measurement which will make it look like hypoT4 with a very high TSH and very low T4
**BUT THE PATIENT IS NORMAL AND THE TEST IS WRONG**
If this is the case... stop taking biotin, redo the tests and they should be normal
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How to treat hypoT4?
**Synthetic thyroid hormones:**
SYNTHROID (L-Thyroxine) --\> T4
Triiodotyronine (Cytomel ) --\> T3
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L-Thyroxine:
Half-life: 7 days
DIE
4-6 weeks for it to stabilize in the blood
Dose varies depending on age and condition of patient
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How to treat older patient or patient with coronary disease for hypoT4?
Start with a small dose and increase very slowly otherwise risk of exacerbating angina or causing an infarctus
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Which medications can you not take with synthroid?
Calcium and iron
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L-Thyroxine in pregnant women:
Primary hypoT4: TSH in normal for first trimester
Central hypoT4: TSH (non fiable), FT4 between normal and the high limits of normal, absence of sx
Check labs 4 weeks after dose adjustment
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Information about triiodothyronine
Half-life: short
Must be taken multiple times a day
Taking with L-Thyroxine is very controversial right now
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What is Hashimotos?
Type of thyroiditis
Immune disorder (anti-TPO)
Infiltration of the thyroid by lymphocytes
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What are the signs and sx of Hashimotos?
Classic hypoT4 sx
Goitre is frequent but possible for the thyroid to have atrophied and become non-palpable
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How does Hashimotos present during investigations?
TSH high
FT4 low
TT3 normal to low
Anti-TPO +++
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How to treat Hashimotos?
Synthroid
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What is a myxedema coma?
Very severe hypoT4
Other factor usually present that makes things worse:
* Infection such as pneumonia
* Exposition to cold
* Acute CV disease: infarctus, ACV
Used to be 50% mortality rate but getting better
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What can cause a myxedema coma?
Untreated hypoT4 or stopping treatment
Presents as normal sx and signs of hypoT4 + altered cognitive function (lethargia, +++ slowed, coma, convulsions)
* hypothermia, hypotension, hypoxemia/hypercapnea, hypoglycemia, hynonatremia
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What are the most common kinds of benign thyroid nodules?
Cysts
Chronic focalized thyroiditis (Hashimotos, granulomateuse)
Focalized hyperplasia
Follicular adenoma
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What are the most common kinds of malignant thyroid nodules?
**Papillary cancer (80%) --\> MOST COMMON**
Follicular cancer (10%)
Medullairy cancer (5%)
**Anaplasic cancer (3%) --\> MOST DANGEROUS**
Lymphoma and metastasis of other cancers (1-2%)
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How to distinguish malignant vs benign thyroid nodules?
History:
* Dysphonia, dysphagia, obstruction --\> more likely malignant
* Fast-growing --\> more likely malignant
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What are some risk factors for thyroid cancer?
Radiation during childhood
Family history
Homme \> femme (if you find nodule in man its more likely to be cancer but incidence of cancer is the same)
Examen physique:
* Hard and immobile
* Adjacent adenopathy
* Large nodule (\> 4cm)
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Labs and scinti for thyroid nodules:
Labs:
* TSH high --\> hypoT4
* TSH normal
* TSH low --\> nodule chaud/autonome (rarely cancerous)
Scinti:
* Nodule froid --\> 5% chance of cancer
* Nodule tiède/chaud --\> cancer rare
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What signs on an echo suggest thyroid cancer?
**NOT CONFIRMATION, SUGGESTION**
Hypoechogenicity (darker than usual)
Microcalcifications
Irregular borders
Nodule higher than bigger
If spongiform --\> 100% benign
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What is a thyroid fine-needle aspiration biopsy?
Distinguish benign, malignant, and follicular (20% malignant)
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Follow-up for thyroid nodules after thyroid fine-needle aspiration biopsy:
Benign: follow-up with palpation, TSH, and echo
Malignant: hemithyroidectomy vs full thyroidectomy
Indeterminate: depending on the patient, dx surgery vs. tight follow-up and aspirations
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What are differentiated thyroid cancers?
Come from follicular cells
Conserve their capacity to secrete TGB --\> becomes cancer marker
Conserve their ability to capture iodine but less efficiently than normal so you can still tx with I-131
**Prognostic: excellent (papillary 98% and follicular 92%)**
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What are the two "forms" of differentiated thyroid cancers?
Papillaire: cellules arrangées sous forme de papilles
Folliculaires: cellules arrangées sous forme de follicules
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Why would someone with differentiated thyroid cancer die from cancer if the prognostic is so good?
Local invasion/compression of the trachea
Pulmonary metastasis --\> insuffisance respiratoire
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How to treat differentiated thyroid cancer?
1. Total/hemithyroidectomy
2. Radioactive iodine
3. Thyroid hormones
Chemo isnt really used
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What is medullary thyroid cancer?
Cellules C --\> parafollicular cancer
Secrete calcitonin
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What is anaplastic thyroid cancer?
aggressive form of thyroid cancer characterized by uncontrolled growth of cells in the thyroid gland
very poor prognosis due to its aggressive behaviour and resistance to cancer treatments
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Signs during patient history that'll point you towards anaplastic thyroid cancer:
F \> H
Age around 65
History of goitre +++
Fast growth thyroid (changes visible day by day)
Dysphagia, dysphonia, and local pressure
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How to treat anaplastic thyroid cancer?
VERY AGRESSIVE TREATMENT OR PALLIATIVE CARE:
Aggressive treatment:
* Total thyroidectomy
* External radiotherapy
* Chemotherapy
Palliative treatment: goal of avoiding unnecessary treatments but try to maintain the patients quality of life
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What is the ddx for thyroid pain?
Subacute thyroiditis
Hemorrhage of thyroid nodule
Trauma (or I-133 treatment)
Abscess
Cancer (quite rare to be painful)
