Anatomy & Histology
A 9-year old boy is brought to the pediatrician because of a neck mass. The patient says the mass appeared 1 week ago and is slightly tender. He recently recovered from an URI. Temperature is 97.6F, pulse is 70/min, and blood pressure is 110/70 mmHg. On examination, a soft mass is palpated in the midline of the neck just superior to the larynx and moves when the patient is asked to stick out his tongue. Which of the following is the most likely diagnosis?
thyroglossal duct cyst
The binding of thyroid hormones intracellularly upregulates the integration of Na+/K+ ATPase pumps into cell membranes. What vital clinical finding is compensatory for this biophysiological change?
Increased respiratory rate
A 35 year old woman presents to clinic with new onset diarrhea and weight loss. Physical exam shows hyperreflexia, and swelling in both lower extremities. Vitals show tachycardia and hypertension. Labs are positive for thyroid stimulating immunogloblulins. The edema caused by this patient’s condition is caused by the activation of what cells by TSH?
Fibroblasts
DAILY DOUBLE: A 24-year-old patient with a history of childhood leukemia presents with a painless thyroid nodule. A fine-needle biopsy is performed and shown below. What is the most likely diagnosis? [PICTURE IN SLIDES]
Papillary thyroid carcinoma
Propranolol is often used as first-line symptom control for patients with thyrotoxicosis. Although atenolol is also a beta-blocker, why is propranolol considered more effective?
Propranolol inhibits 5’-deiodinase
A clot forms in the thyrocervical trunk. As a result, the artery that courses near the recurrent laryngeal nerve in the tracheoesophageal groove would lose blood supply.
inferior thyroid artery
DAILY DOUBLE!!!: Name the 3 anions that competitively inhibit iodide uptake at the Na+/I- symporter
Perchlorate, Pertechnetate, and Thiocyanate
A 43 year old female presents to clinic with new onset fatigue, weight gain, and constipation. She was recently diagnosed with atrial fibrillation by her cardiologist 2 months ago and was prescribed a medication that she takes daily but does not remember the name or dose. Physical exam is unremarkable but vitals are remarkable for bradycardia. Labs show decreased T3/T4 and an elevated TSH. You suspect that these findings are caused by her new cardiac drug. By what two mechanisms does this drug act to cause this patient’s symptoms?
Excess iodine → Wolff-Chaikoff Effect & amiodarone mimics T4 inhibiting 5’-deiodinase
A 45-year-old patient presents with a solitary thyroid nodule. Biopsy reveals uniform follicular cells forming microfollicles without nuclear grooves and empty-appearing nuclei. Which route of metastasis would this malignancy most likely use?
Hematogenous spread
A 45 year old female patient arrives to clinic with a chief complaint of mild weight loss, diarrhea, and palpitations. She has recently undergone radioactive iodine ablation and was placed on Liothyronine 25 mcg daily. Your attending begins to curse under her breath calling her other doctor “incompetent”. She then places the patient on levothyroxine instead and removes the liothyronine. What is the reason for this switch?
Liothyronine is a synthetic form of T3, and can cause mild hyperthyroidism
A child presents with recurrent infections, hypocalcemia, and abnormal thyroid histology lacking parafollicular cells. These findings most likely result from abnormal development of which pharyngeal pouches?
third and fourth pharyngeal pouches
A 23 year-old patient arrives to the free clinic while you are doing a medical mission trip in an impoverished, rural area of Djibouti. PMHx is notable for asthma and chief complaint is for a bothersome mucus-producing cough for the past week. Patient also reveals a long-term history of fatigue and cold-intolerance On physical exam you note a slightly enlarged anterior neck mass, and non-pitting edema. The on-site attending gives them a high dose of SSKI and sends them home. They return 3 days later in a state of delirium, with tachycardia and hyperglycemia. The normal protective physiological effect failed in this patient. What stage of hormone production does this protective effect typically inhibit?
Organification
An 8 month old infant presents to clinic in Davie, FL as his mother is concerned that he is “smaller than average.” Growth parameters are below the 5th percentile, and physical exam reveals a protruding tongue, small forehead with full cheeks, and a “lump” at the umbilicus. A thyroid panel shows markedly increased TSH but decreased total T3 and T4. Nuclear studies reveal NO thyroid abnormalities or ectopic tissues. What is the most likely cause for this infants condition?
Thyroid Dyshormonogenesis; most commonly dysfunction of TPO gene
A patient with a family history of pheochromocytoma and hyperparathyroidism presents with a thyroid mass. Which malignancy is most likely and what molecular mutation is responsible?
Medullary thyroid carcinoma due to a RET proto-oncogene mutation
DAILY DOUBLE!!!: A 35 year old male arrives to clinic with a new onset of a skin rash and a suspected upper respiratory tract infection. He was diagnosed with Grave’s disease last week and is scheduled for a thyroidectomy in 3 months. He has been placed on medications in the meantime to suppress his thyroid until definitive treatment can be done. What class of medication could be responsible for his new symptoms?
Thionamides
What is the function of the hormone produced by the pale-staining cells indicated by arrow A and name one way in which it achieves this effect? [PICTURE IN SLIDES]
decreasing serum calcium via: inhibiting osteoclasts, increasing Ca2+ secretion in urine, or inhibiting renal reabsorption of calcium and phosphorus
A 55 year old man arrives to clinic with a 42 year history of alcohol abuse. PMHx shows patient has a 3 year history of cirrhosis. Physical exam reveals jaundice, caput medusa, and ascites. The attending asks you to order a thyroid panel to determine the prognosis for the patient. What do you expect the values of total T4 to be compared to free T4 and why?
Total T4 is decreased, free T4 is normal. This is due to decreased levels of TBG.
A 55 year old male presents to clinic with chronic generalized, dull abdominal pain that radiates to his back. He states the pain is episodic. Physical exam reveals slight jaundice and lab findings are notable for a slightly elevated lipase and amylase, increased ALP, and increased CRP. The proteins associated with this patient’s condition are also found in which other endocrine-related disease?
Riedel’s Thyroiditis
A 45-year-old patient presents with a solitary thyroid nodule. Fine-needle aspiration reveals uniform follicular cells arranged in microfollicular patterns without nuclear features of papillary carcinoma. The pathologist states that malignancy cannot be determined from this sample. Why is definitive diagnosis not possible from fine-needle aspiration alone?
Distinguishing follicular adenoma from carcinoma requires evaluation of capsular invasion, which cannot be assessed on FNA
A male baby is born to a 37 year old woman via C-section in rural Guatemala, but immediately after birth has respiratory complications including choking and vomiting. Doctors are unable to pass an NG tube into the stomach. The baby dies. PMHx of the mother is notable but Grave’s disease, but she states she has been “taking medications for it everyday”. What medication should the patient have been on to avoid this tragedy?
Propylthiouracil
A thyroid specimen demonstrates disrupted follicular architecture with germinal centers and lymphocytic infiltration. The remaining follicles are atrophic with oncocytic metaplasia. Name the altered epithelial cell type.
BONUS (+50): which thyroid condition is associated with these histopathologic changes? [PICTURE IN SLIDES]
Hurthle cells
A 24 year old female arrives to your clinic with new onset anxiety, palpitations, and insomnia for the past 2 months. Her BP is 134/85, and pulse is 100 bpm. She has no other PMHx. She states she has been feeling hungrier lately, and notes a slight increase in weight of 5 lbs over the past 2 months. She is not on any medications and denies OCP’s, but admits to multiple sexual partners. The attending orders routine lab workups and it is notable for a normal TSH but elevated total serum T4. What is the primary reason for this patient’s abnormal lab findings?
Pregnancy; hCG stimulates the thyroid, and increased estrogen increases TBG levels
A 40 year old woman presents to the clinic with new-onset tachycardia, excessive sweating, and issues falling asleep over the past 2 weeks. Physical exam reveals a painless, palpable mass at the anterior midline of the neck. No notable PMHx. Suspecting a possible neoplasm you perform a fine-needle aspiration and prescribe propranolol. However, histology reveals no signs of dysplasia, hyperplasia, or indications of neoplasms. During the 3 month follow up visit, the patient states that her previous symptoms are no longer bothering her, but she has gained 8 pounds despite not changing her diet and now hates being in her office as they always “blast the A/C”. What is the reason for the initial presentation of this patient’s most likely disease?
Release of thyroid hormones due to inflammatory destruction of thyroid follicles
A 38-year-old patient presents with chronic watery diarrhea and a thyroid mass. Laboratory studies reveal:
Serum calcium: 7.2 mg/dL
Serum phosphate: mildly elevated
Parathyroid hormone: elevated
25-OH vitamin D: normal
TSH: normal
Core biopsy of the thyroid lesion demonstrates nests of neuroendocrine cells with extracellular eosinophilic material in the stroma. What is the most likely diagnosis, and explain the mechanism responsible for the laboratory abnormalities.
Medullary thyroid carcinoma which secretes calcitonin
A 17 year old female arrives to clinic with new-onset throat pain. She states that 2 weeks ago she had “the worst cold he’s experienced in his life”. Despite the cold symptoms subsiding, she feels like her heart is racing and she has trouble sleeping as well as being “hungry all the time”. She is worried she is still sick and wants antibiotics. Physical exam shows an enlarged, tender, movable mass on the anterior neck. What class of medications would be the next best step to managing this patient’s condition?
Anti-inflammatories ex. NSAIDs or steroids