Endocrine Review Flashcards
Blood Supply to Thyroid
Superior Thyroid Artery (first branch of external carotid artery)
Inferior Thyroid Artery (off thyrocervical trunk)
Ima (occurs in 1%, off innominate or aorta and supplies isthmus)
Blood supply to Parathyroids
Inferior thyroid artery
Venous drainage of thyroid
Superior thyroid vein - drain into IJ
Middle thyroid vein - drain into IJ
Inferior thyroid vein - drain into innominate vein
Feedback loop for thyroid hormone production
Thyrotropin releasing factor from hypothalamus acts on anterior pituitary to release TSH
TSH acts on thyroid to release T3 and T4 (by increasing cAMP)
What does recurrent laryngeal nerve supply
Motor to all larynx except cricothyroid muscle
What does superior laryngeal nerve supply
Motor to cricothyroid muscle
Anatomy of Recurrent laryngeal nerve
Runs posterior to thyroid lobe in tracheoesophageal grove
Left RLN loops around aorta
Right RLN loops around innominate artery
Anatomy of superior laryngeal nerve
Tracks close to superior thyroid artery but is variable
Injury to recurrent laryngeal nerve
Hoarsness
Bilateral -> airway obstruction (consider tracheostomy)
Injury to superior laryngeal nerve
Loss of voice projection and voice fatigability (Opera Singers)
Role of thyroglobulin
Stores T3 and T4 in colloid, (Plasma T4 ratio is 15x greater than T3)
T3 is active form
T3 production in periphery
Conversion by deiodinases which separate iodine from tyrosine
Thyroid Storm Symptoms and Presentation
Symptoms: tachycardia, fever, high output cardiac failure
Presentation: surgery in patient w/ undiagnosed Graves
Thyroid Storm Treatment
Beta blockers Lugol's solution (Potassium iodine) - to inhibit TSH action on thyroid Cooling blankets Oxygen Glucose
Diffuse enlargement of thyroid without evidence of functional abnormality - treatment
Thyroxine
Subtotal vs total thyroidectomy if failure of medial management
Midline cervical mass between hyoid bone and thyroid isthmus
Thyroglossal duct cyst - moves upward with swallowing, can be susceptible to infection, maybe be pre-malignant
Tx: resect with mid portion of hyoid bone (sistrunk procedure)
Treatment for hyperthyroidism
Methimazole (causes cretinism in pregnancy) or
PTU (Safe in pregnancy)
Both inhibit peroxidase to prevent iodine-tyrosine coupling
Side effect: aplastic anemia, agranulocytosis
Most common cause of hyperthyroidism
Graves - due to IgG to TSH receptor
Diagnosed by decreased TSH, increased T3, T4, increased/diffuse iodine uptake
Treatment of Graves
Thioamides, radioactive iodine, or thyroidectomy
Pre-op must have methimazole until euthyroid, beta-blockers and lug’s solution for 2 weeks prior to decrease friability and vascularity
Most common cause of hypothyroidism in adults
Hashimoto’s disease caused by humeral and cell-mediated autoimmune disease
pathology = lymphocytic infiltrate
Treatment of graves
Thyroxine (first line)
Partial thyroidectomy if fails medical treatment
Presentation of De Quervain’s
Viral URI –> tender thyroid, weakness, fatigue, increased ESR
Riedel’s fibrous struma
Woody, fibrous component involving thyroid, strap muscles and carotid sheath, can cause compressive symptoms
Tx w/ steroids and thyroxine
Risk factors for Papillary thyroid cancer
Childhood XRT
Pathology of Papillary Thyroid Cancer
Psammoma bodies (calcium) Orphan Annie Nuclei
Spread of Papillary Thyroid Carcinoma
Lymphatic first
Local invasion is most prognostic
Rarely mets to lungs
Risk factor for Follicular thyroid carcinoma
Older women
Spread of Follicular thyroid carcinoma
Hematogenous spread (bone most common), 50% have metastatic disease at presentation
Treatment for papillary and follicular thyroid cancer
Total thyroidectomy if >1cm, extra thyroidal disease, multi-centric or prior XRT
Do modified radical neck dissection for extra-thyroidal disease
Post op radiactive iodine if tumor >1cm or extra thyroidal disease
Etiology of Medually Thyroid Carcinoma
Associated w/ MEN IIa or IIb (RET proto-oncogene) but 80% sporadic
Occurs in parafollicular C cells which secrete calcitonin
present w/ flushing and diarrhea
Pathology of Medullary thyroid carcinoma
amyloid deposition
Spread of medullary thyroid
Lymphatic spread (most have nodes at time of diagnosis)
early mets to lung, liver, bone
Treatment of medullary thyroid cancer
Total thyroidectomy w/ central neck dissection
When to do thyroidectomy in Men IIa vs IIb
IIa - 6 years
IIb - 2 years
Pathology of Anaplastic Thyroid Cancer
Vesicular appearance of nuclei
Treatment of anapestic thyroid cancer
Palliative thyroidectomy vs chemo-XRT for compressive symptoms
Pathology of Hurtle cell carcinoma
Ashkenazi cells - you cannot determine benign vs malignant on biopsy alone, requires lobectomy
If malignant do total thyroidectomy
Which subtypes of thyroid cancer is radioactive iodine effective for
Papillary and follicular thyroid cancer only
Indications are recurrent cancer, >1cm or extra thyroidal disease
