Voiceiver: Welcome to NP Certification Q&A presented by Fitzgerald Health Education Associates. This podcast is for NP students studying to pass their NP certification exam. Getting to the correct test answers means breaking down the exam questions themselves. Leading NP expert Dr. Margaret Fitzgerald shares her knowledge and experience to help you dissect the anatomy of a test question so you can better understand how to arrive at the correct test answer. So, if you're ready, let's jump right in.
Margaret Fitzgerald: A 50-year-old woman presents for follow-up on recent lab tests obtained at a health maintenance visit. She reports feeling well and denies fatigue, weight changes, constipation, cold intolerance, palpitations, or changes in mood. She was recently diagnosed with subclinical hypothyroidism. Which of the following would be her expected lab results?
A. TSH of 8.6, elevated free T4 of 14, which is normal.
B. TSH of less than 0.15, undetectable a free T4 of 79, marketkedly elevated
C. TSH of 24, elevated a free T4 of three, marketkedly reduced
D. TSH of 1.8, which is normal, and a free T4 of 14, also normal
The correct answer is a TSH of 8.6 and a free T4 of 14.
Where do you start with a question like this? First, determine what kind of a question it is. Here we're given her diagnosis, but then we're asked for what laboratory values we would see in this patient that would help us confirm that diagnosis. And so it's actually it's an assessment question. A bit of background information, subclinical hypothyroidism, often abbreviated SCH, is a mild form of early hypothyroidism. The condition is often detected when laboratory testing is done as part of evaluation of fatigue or a mood disorder or some other type of clinical presentation that is not thyroid specific.
In this case, we're actually not told why she had the lab testing done, but we're just given the information that she has this diagnosis. So, we need to run with that. With subclinical hypothyroidism, the thyroid requires a little bit more than typical stimulation with TSH, thyroid stimulating hormone to produce an acceptable amount of thyroid hormone release. And that is because the thyroid is failing. As with other thyroid disease, subclinical hypothyroidism is usually autoimmune in origin. Eventual thyroid failure and resulting hypothyroidism usually follows particularly if there is evidence of TPO antibodies.
TPO antibodies are a marker of autoimmune thyroid disease. There's about a 2 to 5% likelihood of developing overt hypothyroidism per year with subclinical hypothyroidism particularly with the presence of the TPO antibodies.
One way of thinking of this with subclinical hypothyroidism is that if you will, you've caught the thyroid as it is failing, but the thyroid still has enough function in it that with a little bit extra stimulation, a little bit extra TSH, the free T4 will be normal. What happens more often? You pick up thyroid failure in clinical practice when the patient presents with overt hypothyroidism. But also keep in mind, what does thyroid hormone do? Free T4. It acts as a cellular energy release catalyst to every single cell in the human body. And that's why the presentation of hypothyroidism is so diffuse. But at the same time, many of the findings with overt hypothyroidism are quite non-specific to thyroid disease like fatigue, dry skin and the like. But then we have a few findings that are more specific to it like diffuse hyporeflexia and the like.
Prior to age 60, subclinical hypothyroidism, indeed almost any form of thyroid disease, is found primarily in females. Once once hitting age 60, the number of males with any kind of thyroid disease does increase. Once again, the clinical presentation of subclinical hypothyroidism is non-specific and where the patient either feels well or there's some common complaints that aren't necessarily associated with thyroid disease. Abnormalities in the thyroid exam with subclinical hypothyroidism are rare as are alterations in the DTRs.
How is this condition diagnosed? It's diagnosed just as we're seeing here, elevated TSH with a normal free T4 in the absence of or minimal symptoms. Testing for TPO antibodies, that clinical marker of autoimmune thyroid disease that I just mentioned, is advised to help make the decision on whether to initiate uh T4 therapy, levothyroxine now or wait. The treatment of subclinical hypothyroidism varies on a number of factors. Again, the presence or absence of these TPO antibodies, the degree of TSH elevation, whether pregnancy or imminent pregnancy is a consideration, and a number of other factors. I'll get to this in a future podcast.
With this in mind, let's take another look at the question in possible responses. A 50-year-old woman presents for follow up on recent lab tests obtained at a health maintenance visit. She reports feeling well and denies fatigue, weight gain, constipation, cold intolerance, palpitation, or changes in mood. She was recently diagnosed with subclinical hypothyroidism. Which of the following would be her expected lab results?
A. TSH of 8.6, mildly elevated and a free T4 of 14, which is normal. This is of course the correct answer. Here we have the classic presentation of subclinical hypothyroidism where the free T4 perfectly normal, but the thyroid is in the process of failing and therefore the anterior lobe of the pituitary picks up on this. Make sure there's a little extra TSH, thyroid stimulating hormone on board to keep that thyroid working. A person usually feels well because there is that normal amount of free T4 in circulation. General rule with subclinical hypothyroidism at bare minimum rechecking these values in about six months would be next step.
Option B, TSH of less than 0.15 or non-detectable and a free T4 of 79, marketkedly elevated. And by the way, that free T4 is about three times upper limits of normal. Here we have the classic presentation of hyperthyroidism. And what's happening here is a thyroid is throwing off hormone on its own. Therefore, the anterior lobe of the pituitary says, "Uhoh, thyroid's throwing this hormone out on its own. We do not need to produce a massive TSH to keep that thyroid working." And so therefore, the high levels of free T4 cause a dialing back on the TSH produced. And of course, if this person had clinical hyperthyroidism, you would get all those signs and symptoms of this elevated heart rate, tremor, hyperreflexia, feeling like my heart's going to hop right out of my chest, that type of thing. So, that whole body revved up feeling that people with hyperthyroidism invariably have.
C. TSH of 24 which is elevated TSH, I'm sorry free T4 of three super low this is the classic presentation of hypothyroidism the thyroid has failed and even with extra activation from TSH the poor little dead/dying thyroid can't get enough free T4 out into circulation, that person likely would have signs and symptoms of hypothyroidism. And just to throw that in one more time, one fairly specific finding in hypothyroidism is diffuse hyporeflexia.
Last option D, the TSH is 1.8, which is within normal limits. Free T4 is 14 also within normal limits. Here we have normal lab values. Clearly, this is a person who does not currently have thyroid disease.
Key takeaway and diagnosing all forms of thyroid disease. The TSH and the free T4 must always be interpreted together. This reflects the relationship between the pituitary and the thyroid and helps distinguish normal thyroid function, subclinical disease and overt thyroid dysfunction.
Voiceover: Thank you for listening to NP Certification Q&A presented by Fitzgerald Health Education Associates. Please rate, review, and subscribe to this podcast. And for more NP resources, visit fhea.com.
