{"version":"1.0.0","segments":[{"startTime":0.0,"endTime":3.12,"body":"[music]"},{"startTime":3.12,"endTime":5.53,"body":"(Cathy) Hi, welcome to \u003ci\u003eHarrison's Podclass\u003c/i\u003e"},{"startTime":5.53,"endTime":8.53,"body":"where we discuss important concepts"},{"startTime":5.53,"endTime":8.53,"body":"in internal medicine."},{"startTime":8.53,"endTime":10.85,"body":"- I'm Cathy Handy."},{"startTime":8.53,"endTime":10.85,"body":"- And I'm Charlie Wiener,"},{"startTime":10.85,"endTime":14.1,"body":"and we're coming to you"},{"startTime":10.85,"endTime":14.1,"body":"from the Johns Hopkins School of Medicine."},{"startTime":15.87,"endTime":17.94,"body":"Welcome to \u003ci\u003eHarrison's Podclass.\u003c/i\u003e"},{"speaker":"This is Episode 3","startTime":17.94,"endTime":23.27,"body":"A 23-Year-Old"},{"speaker":"This is Episode 3","startTime":17.94,"endTime":23.27,"body":"with an undetectable TSH."},{"speaker":"Our question","startTime":23.27,"endTime":26.548,"body":"A 23-year-old college student"},{"speaker":"Our question","startTime":26.548,"endTime":28.458,"body":"is followed in the student health center"},{"speaker":"Our question","startTime":28.458,"endTime":31.618,"body":"for medical management"},{"speaker":"Our question","startTime":28.458,"endTime":31.618,"body":"of panhypopituitarism"},{"speaker":"Our question","startTime":31.618,"endTime":35.208,"body":"after resection of a"},{"speaker":"Our question","startTime":31.618,"endTime":35.208,"body":"craniopharyngioma as a child."},{"speaker":"Our question","startTime":35.208,"endTime":38.008,"body":"She reports moderate compliance"},{"speaker":"Our question","startTime":35.208,"endTime":38.008,"body":"with her medications"},{"speaker":"Our question","startTime":38.008,"endTime":40.298,"body":"but feels generally well."},{"speaker":"Our question","startTime":40.298,"endTime":43.708,"body":"Thyroid stimulating hormone, TSH is checked"},{"speaker":"Our question","startTime":43.708,"endTime":46.968,"body":"and it's below the limits of detection"},{"speaker":"Our question","startTime":43.708,"endTime":46.968,"body":"of the assay."},{"speaker":"Our question","startTime":46.968,"endTime":50.208,"body":"Which of the following is the next"},{"speaker":"Our question","startTime":46.968,"endTime":50.208,"body":"most appropriate action?"},{"speaker":"Our question","startTime":50.208,"endTime":55.778,"body":"a) Decrease levothyroxine dose"},{"speaker":"Our question","startTime":50.208,"endTime":55.778,"body":"to half of the current dose."},{"speaker":"Our question","startTime":55.78,"endTime":58.27,"body":"b) Do nothing."},{"speaker":"Our question","startTime":58.28,"endTime":61.23,"body":"c) Order a free T4 level."},{"speaker":"Our question","startTime":61.74,"endTime":64.92,"body":"d) Order an MRI of her brain."},{"speaker":"Our question","startTime":64.92,"endTime":68.83,"body":"or e) order a thyroid uptake scan."},{"speaker":"Our question","startTime":68.83,"endTime":71.3,"body":"So, Cathy, what are your thoughts"},{"speaker":"Our question","startTime":68.83,"endTime":71.3,"body":"on this case?"},{"speaker":"Our question","startTime":71.3,"endTime":73.63,"body":"(Cathy) The major things to note here"},{"speaker":"Our question","startTime":71.3,"endTime":73.63,"body":"are that the patient's young"},{"speaker":"Our question","startTime":73.63,"endTime":78.05,"body":"and she's relied on exogenous pituitary"},{"speaker":"Our question","startTime":73.63,"endTime":78.05,"body":"hormone since her childhood surgery."},{"speaker":"Our question","startTime":78.05,"endTime":80.65,"body":"She's also been able to live"},{"speaker":"Our question","startTime":78.05,"endTime":80.65,"body":"a relatively normal life"},{"speaker":"Our question","startTime":80.65,"endTime":83.63,"body":"with diligent management"},{"speaker":"Our question","startTime":80.65,"endTime":83.63,"body":"of her hormonal replacement."},{"speaker":"Our question","startTime":83.63,"endTime":85.71,"body":"In addition to thyroid"},{"speaker":"Our question","startTime":83.63,"endTime":85.71,"body":"replacement in patients"},{"speaker":"Our question","startTime":85.71,"endTime":87.38,"body":"who've had their pituitary removed,"},{"speaker":"Our question","startTime":87.38,"endTime":90.94,"body":"it's important to remember that in times"},{"speaker":"Our question","startTime":87.38,"endTime":90.94,"body":"of significant physiologic stress"},{"speaker":"Our question","startTime":90.94,"endTime":94.94,"body":"like an acute illness, she may"},{"speaker":"Our question","startTime":90.94,"endTime":94.94,"body":"also require stress dose steroids."},{"speaker":"Our question","startTime":94.94,"endTime":98.27,"body":"(Charlie) What do you make of"},{"speaker":"Our question","startTime":94.94,"endTime":98.27,"body":"the undetectable TSH in her case?"},{"speaker":"Our question","startTime":98.27,"endTime":101.0,"body":"(Cathy) So, going over the thyroid"},{"speaker":"Our question","startTime":98.27,"endTime":101.0,"body":"hormone access loop,"},{"speaker":"Our question","startTime":101.0,"endTime":103.87,"body":"you remember that"},{"speaker":"Our question","startTime":101.0,"endTime":103.87,"body":"the hypothalamus makes TRH"},{"speaker":"Our question","startTime":103.87,"endTime":106.86,"body":"which stimulates the pituitary"},{"speaker":"Our question","startTime":103.87,"endTime":106.86,"body":"to make TSH,"},{"speaker":"Our question","startTime":106.86,"endTime":110.37,"body":"and then that acts on the thyroid"},{"speaker":"Our question","startTime":106.86,"endTime":110.37,"body":"to make T4 and T3."},{"speaker":"Our question","startTime":110.37,"endTime":114.04,"body":"All of these are in a feedback loop"},{"speaker":"Our question","startTime":110.37,"endTime":114.04,"body":"so TSH from the pituitary"},{"speaker":"Our question","startTime":114.04,"endTime":118.46,"body":"feeds back on the hypothalamus"},{"speaker":"Our question","startTime":114.04,"endTime":118.46,"body":"and downregulates the production of TRH,"},{"speaker":"Our question","startTime":118.46,"endTime":123.129,"body":"and then, T4 and T3 feed back on"},{"speaker":"Our question","startTime":118.46,"endTime":123.129,"body":"the pituitary and downregulate TSH."},{"speaker":"Our question","startTime":123.129,"endTime":125.079,"body":"So, getting back to"},{"speaker":"Our question","startTime":123.129,"endTime":125.079,"body":"the question that you asked"},{"speaker":"Our question","startTime":125.079,"endTime":127.439,"body":"about the undetectable TSH in this case,"},{"speaker":"Our question","startTime":127.439,"endTime":129.689,"body":"since the patient doesn't"},{"speaker":"Our question","startTime":127.439,"endTime":129.689,"body":"have a pituitary gland"},{"speaker":"Our question","startTime":129.689,"endTime":133.509,"body":"she won't produce TSH, so really,"},{"speaker":"Our question","startTime":129.689,"endTime":133.509,"body":"here it's not helpful at all."},{"speaker":"Our question","startTime":133.509,"endTime":135.249,"body":"(Charlie) What about utilizing TSH"},{"speaker":"Our question","startTime":135.249,"endTime":138.289,"body":"to monitor thyroid function"},{"speaker":"Our question","startTime":135.249,"endTime":138.289,"body":"in a normal patient?"},{"speaker":"Our question","startTime":138.289,"endTime":141.329,"body":"(Cathy) So, in a normal patient,"},{"speaker":"Our question","startTime":138.289,"endTime":141.329,"body":"TSH is what you would use."},{"speaker":"Our question","startTime":141.329,"endTime":145.689,"body":"And we use it mostly to screen"},{"speaker":"Our question","startTime":141.329,"endTime":145.689,"body":"for hyperthyroidism or hypothyroidism,"},{"speaker":"Our question","startTime":145.689,"endTime":148.138,"body":"or in a patient who's"},{"speaker":"Our question","startTime":145.689,"endTime":148.138,"body":"on thyroid replacement"},{"speaker":"Our question","startTime":148.138,"endTime":150.238,"body":"because of a primary thyroid disorder."},{"speaker":"Our question","startTime":150.238,"endTime":154.238,"body":"You would also use it to measure"},{"speaker":"Our question","startTime":150.238,"endTime":154.238,"body":"the adequacy of thyroid replacement."},{"speaker":"Our question","startTime":154.238,"endTime":156.488,"body":"If TSH is undetectable that means that"},{"speaker":"Our question","startTime":156.488,"endTime":158.428,"body":"there's too much"},{"speaker":"Our question","startTime":156.488,"endTime":158.428,"body":"thyroid hormone replacement;"},{"speaker":"Our question","startTime":158.428,"endTime":160.118,"body":"and if it's elevated,"},{"speaker":"Our question","startTime":160.118,"endTime":162.428,"body":"that means that there's not enough"},{"speaker":"Our question","startTime":160.118,"endTime":162.428,"body":"hormone replacement."},{"speaker":"Our question","startTime":162.428,"endTime":166.428,"body":"Therefore, the answer in this case is C;"},{"speaker":"Our question","startTime":162.428,"endTime":166.428,"body":"that you want to measure the free T4."},{"speaker":"Our question","startTime":166.428,"endTime":169.298,"body":"And you would also want to know"},{"speaker":"Our question","startTime":166.428,"endTime":169.298,"body":"if she's having any symptoms"},{"speaker":"Our question","startTime":169.298,"endTime":171.998,"body":"related to hyper or hypothyroidism."},{"speaker":"Our question","startTime":171.998,"endTime":173.778,"body":"(Charlie) What about the other answers?"},{"speaker":"Our question","startTime":173.778,"endTime":176.608,"body":"Is there any role of the imaging"},{"speaker":"Our question","startTime":173.778,"endTime":176.608,"body":"in patients such as this?"},{"speaker":"Our question","startTime":176.608,"endTime":177.828,"body":"(Cathy) Not in this case."},{"speaker":"Our question","startTime":177.828,"endTime":179.038,"body":"MRI would be useful"},{"speaker":"Our question","startTime":179.038,"endTime":182.698,"body":"if you thought that there was a new or"},{"speaker":"Our question","startTime":179.038,"endTime":182.698,"body":"a recurrent intracranial process."},{"speaker":"Our question","startTime":182.698,"endTime":185.608,"body":"It may have been used"},{"speaker":"Our question","startTime":182.698,"endTime":185.608,"body":"when she initially presented."},{"speaker":"Our question","startTime":185.608,"endTime":188.768,"body":"And a thyroid uptake scan,"},{"speaker":"Our question","startTime":185.608,"endTime":188.768,"body":"you would use mostly for a suspicion"},{"speaker":"Our question","startTime":188.768,"endTime":191.668,"body":"of thyroid disease"},{"speaker":"Our question","startTime":188.768,"endTime":191.668,"body":"such as autoimmune thyroiditis."},{"speaker":"Our question","startTime":191.668,"endTime":193.648,"body":"Neither of those apply in this case."},{"speaker":"Our question","startTime":193.648,"endTime":194.818,"body":"(Charlie) That's great, Cathy."},{"speaker":"Our question","startTime":194.818,"endTime":198.907,"body":"So, in this case the answer is C,"},{"speaker":"Our question","startTime":194.818,"endTime":198.907,"body":"order a free T4 level"},{"speaker":"Our question","startTime":198.907,"endTime":202.457,"body":"because the undetectable TSH"},{"speaker":"Our question","startTime":198.907,"endTime":202.457,"body":"is not helpful"},{"speaker":"Our question","startTime":202.457,"endTime":205.207,"body":"because of the absence of her pituitary."},{"speaker":"Our question","startTime":205.207,"endTime":208.897,"body":"This is a great teaching point that TSH"},{"speaker":"Our question","startTime":205.207,"endTime":208.897,"body":"can be a useful screening test"},{"speaker":"Our question","startTime":208.897,"endTime":212.347,"body":"in most patients, but in patients"},{"speaker":"Our question","startTime":208.897,"endTime":212.347,"body":"without a functioning pituitary"},{"speaker":"Our question","startTime":212.347,"endTime":214.687,"body":"for whatever reason,"},{"speaker":"Our question","startTime":212.347,"endTime":214.687,"body":"surgery or otherwise,"},{"speaker":"Our question","startTime":214.687,"endTime":218.912,"body":"you must go more downstream and measure"},{"speaker":"Our question","startTime":214.687,"endTime":218.912,"body":"the direct measurement of free T4"},{"speaker":"Our question","startTime":218.912,"endTime":221.98,"body":"to measure the adequacy"},{"speaker":"Our question","startTime":218.912,"endTime":221.98,"body":"of a thyroid replacement therapy."},{"speaker":"Our question","startTime":221.98,"endTime":224.01,"body":"(Cathy) It's also important"},{"speaker":"Our question","startTime":221.98,"endTime":224.01,"body":"to remember that in any patient"},{"speaker":"Our question","startTime":224.01,"endTime":226.79,"body":"taking exogenous thyroid"},{"speaker":"Our question","startTime":224.01,"endTime":226.79,"body":"hormone replacement,"},{"speaker":"Our question","startTime":226.79,"endTime":230.68,"body":"it's important to ask about clinical"},{"speaker":"Our question","startTime":226.79,"endTime":230.68,"body":"symptoms in addition to the lab test."},{"speaker":"Our question","startTime":230.68,"endTime":231.87,"body":"And to read more about this,"},{"speaker":"Our question","startTime":231.87,"endTime":235.65,"body":"you can check out Harrison's chapter"},{"speaker":"Our question","startTime":231.87,"endTime":235.65,"body":"on disorders of the thyroid gland."},{"speaker":"Our question","startTime":236.25,"endTime":238.12,"body":"(Charlie) Thank you!"},{"speaker":"Our question","startTime":238.12,"endTime":244.25,"body":"[music]"}]}