Lecture 87/88 -Thyroid path and thyroid disorders Flashcards
what is the fucntional unit of the thyroid? what is produced?
what other hormone is produced in the thyroid and by what cell type?
Follicles – produce colloid (stores of thyroid hormone)
Parafollocular cells (C cells) – Produce calcitonin
_____ is responsible for the formation of thyroid hormone
peroxidase
most thyroid hormone is secreted as ___- and then converted to ___ in the periphery by ____
___ is more biologically active
T4
T3 – more biologically active
5’ Deiodinase
Describe the effects of Thyroid hormone on bone, brain, CV, metabolsim?
○ Bone – activation of ostoclasts
§ FIRST AID: Bone growth and maturation
○ Brain – Stimulates axonal growth and development
○ Blood/CVD – Increased CO, Blood volume and Decreases SVR
§ FIRST AID: Increased B1 adrenergic receptors
Basal Metabolic Rate –
§ Liver – regulates lipid metabolism
§ Fat - increases lipolysis
§ GI – bowel regularity
Etiologies of primary hypothyroid disease
Hashimoto's Post Ablative Iodine Def Transient (post thyroiditis) Congenital
what is the most common cause of hypothyroid
what additional test is important to run if this is suspected?
Hashimoto’s
Autoantiboides: Anti-Thyroid Peroxidase, Anti Thyroglobulin
anticipated labs for primary hypothyroid
high TSH
Low T3/T4
+/- AntiTPO antibodies
Etiologies of Central hypothyroid
Aquired vs congenital deficiencies of pituitary disorders, hypothalamic disorders, TSH deficiency or TSH receptor defect
how can a patient with resistance to the Thyroid hormone present as either hyperthyroid or hypothyroid?
Mutation to the Thyroid Receptor; will depend on how diffuse the mutation is.
If only on Pitutitary – negative feedback is disrupted; pt appears hyper
If diffusely mutation in the periphery – pt not able to respond at all to hormonme; appears hypo
What is a Myxedema coma
what are some of the significant findings?
severe long stanidng hypothyroidism;
may lead to AMS, Bradycardia, heart block, prolonged QT, Hypotension, Delayed DTR relaxation, hypoventilation, Sz
• Hypothyroid In Pregnancy –
possible complications?
maternal – pre-eclampsia, hemorrhage, miscarriage, abruption,
Fetal – low weight, impaired cognition,
what is the gold standard of the thyroid function test?
what are the anticipiated labs for:
1) primary hypo
2) central hypo
3) Thyroid hormone resistance
Free T4
1) Primary hypo: High TSH, low T4
2) Central: Low TSH, Low T4
3) Resistance: High TSH, High T3/4, but no response
what is the difference between thyrotoxicosis and Hyperthyroid
○ Thyroidtoxicosis - physiologic manifestations of excessive quantities of thyroid hormone
○ Hyperthyroidism – Thyroidtoxicosis caused by d/o overproduction of thyroid hormone
signs and symptoms of HyperThyroid- -
what sx might be different between older and younger pts
younger – Sympthatic activation (anxiety, hyperactivity, tremor)
Older – CV symptoms (afib, dyspnea)
General – heat intolerance, weight loss, increased appetite, diarrhea, increased reflexes, insomina, nervousness,
signs and symptoms of hypothyroid
fatigue, lethary, somnolence, weight gain, decreased appetite, cold intolerance, dry skin, hair loss (lateral 1/3 of eye brow)
Most common cause of thyrotoxicosis
underlying pathophysiology
signs and symptoms
Grave’s Disease
Pathophys; IgG activation of the TSH receptor
signs and symptoms:
Peritibial myxedema, Exophthalmos, lid edema, Vitiligo, Dermopathy
Other etiologies of primary hyperthyroid
graves
Toxic MNG
Toxic Adenoma –
Beta HCG
What is the difference between toxic MNG and toxic thyroid adenoma
Toxic MNG – 2 or More Focal patches of Hyper-functioning follicular nodules;
Toxic Adenoma – single hyper functioning nodule
how can beta HCG induce hyperthroid?
Shared Alpha subunit homology with TSH
during pregnancy or trophoblastic tumors
what is a thyroid storm?
is this fatal?
Emergency Hyperthyroid
Stress induced catecholamine surge
Some symptoms can be fatal:
tachyarrythmias, tachypnea,
other: Fevre, AMS, HTN
etiology of secondary hyperthyroid
what other features may also be present?
TSH producing pituitary adenoma
Bi temporal hemianopsia
25% also produce high prolactin
2 situations of transient hyperthyroid
Subactue Thyroiditis – (Quevain’s) ; hyperthyroid early in the course
Post Partum Thyroiditis – hyperthyroid for first few weeks, then hypothyroid for a few months before leveling out
anticipated labs for:
1) primary hyperthyroid
2) secondary hyperthyroid
Primary – high t3/4; low TSH
+/- TSI antibodies
Secondary - -High t/3/4, high TSH
high t3 + positive TSI is indicattive of
Graves disease
first line imaging to help narrow the differentiate of hyperthyroid
what would anticpated results be for :
Graves
Toxic MNG
Thyroiditis
Thyroid Uptake and Scan –
Graves – uptake all over
Toxic MNG – multiple islands of increased uptake
Thyroiditis – no increased uptake (pt is hyperthyroid because inflammation has released all stores of thyroid hormone)
Medical management of hypothyroid patients
§ Levothyroxin (Synthroid) – Synthetic T4 – the main treatment
§ Synthetic T3 – rarely used (much more potent)
medical management of hyperthyroid
drugs + mechanisms
Non selective beta blockers (propranolol –which also exhibits some peripheral t4 conversion)
Antithyroid Drugs:
Mthimazole – blocks peroxidase
PTU - blocks peroxidase and 5’ deiodinase
Thyroid ablation tehcniques
Radioactive Iodine – (I 131) –
Surgery followed by anti-thyroid meds; then followed up thyroid supplements
patient presents with anterior midline mass which moves with swallowing. pathology reports a SCC lining. what is the dx?
Thyroglossal duct cyst
Patients with Hashimotos are at increased risk for____
lymphoma
patient presents with hyperthyroid symptoms 1 week after viral infection; thyroid is inflammated and tender to palpation on exam. what is the dx? what is the likely histological path
Dx; Subacute Thyroiditis
Histo: Patchy distribution;
early – neutrophils
later: giant cells, granulomatous; possible fibrosis
patient presents with a multi nodular goiter and has no sx of hypo or hyper thyroid. how should you proceed?
what are the odds this is malignant?
FNA
Malignant –
patient presents with a multi nodular goiter and has no sx of hypo or hyper thyroid. how should you proceed?
FNA
(hot vs cold) nodules are more likely to be benign
__% of solitary thyroid nodules are malignant
more likely to be malignant if ____ patient
Hot nodules – more likely benign
10% solitary nodules are malignant
higher suspicion of malignancy if young male patient
what cytologic characterisitics on FNA are used to help differentiate between malignant and benign thyroid neoplasms
how do you proceed if malignant
what other classification may be considered
Benign Follicular Neoplasm:
Lots of colloid, Low cellularlity, Macrofollicular
Malignant Suspicion:
Lots of cells, low colloid, Microfollicular
30% malignancy risk
(Tx - Thyroidectomy)
Atypica of Uncertain Significance (AUS);
mixed features;
5-10% risk of malignancy
Management -Repeat the FNA
what is the most common solitary thyroid nodule
Follicular adenoma
Described similar and different pathological findings between Follicular Adenoma vs Follicular Carcinoma
Follicular Adenoma –
Tumor is confined to a well defined thyroid capsule
mixed Macro vs Microfollicular
Follicular Carcinoma -
Tumor with thyroid Capsular and Vascular invasion
Microfollicular; uniform
Both: Hurtle Cell Changes
prognosis and treatment of Follicular carcinoma
Good prognosis –
Tx - Thyroidectomy + RAI
what is the most common thyroid carcinoma
what is the prognosis
how do you treat
Papillary carcinoma
prognosis: Excellent; 90% 10 year survival
Thyroidectomy + RAI
Histological findings of Papillary carcinoma
Psammoma bodies;
Nuclear enalrgement, crowding and overlap
Nuclear Features: Oval Nuclei, Nuclear grooves, overlapping nuclei, Orphan Annie Eyes
which thyroid cacncer has the poorest prognosis
○ Undifferentiated (Anaplastic) Carcinoma – rapidly enlarging
○ Undifferentiated (Anaplastic) Carcinoma
who presents with this?
Common clinical symptoms
gross path
histo path
Older patients (mean: 65 yo)
Symptom: Hoarseness of voice
Gross: large mass invading beyond the thyroid
Histo: highly anaplastic cells, spindled, giant cells
all thyroid cancers are dervied from _____cells, except for ____ which comes from _____
Follicular cells
Exception: medullary carcinoma
C cells (parafollicular)
medullary Carcinoma –
a/w what congenital d/o –
what lab might be elevetaed
some histo findings
MEN2A and 2b (RET mutations)
high calcitonin
Histo: solid sheets of cells iwth amyloid deposition
Lymphoma of the thyroid gland is associated with_____
hashimotos’
tumors of what other organs can met to the thyroid
Lung, Esophagus, Breast, Kidney
rare overall
