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.
A 45-year-old woman with no chronic health problems presents with a six-month history of increasing fatigue, despite opportunity to rest, worsening dry skin, and increased menstrual low volume.
In analyzing the laboratory data below, which is most consistent with the diagnosis of hypothyroidism?
Would it be
A TSH of below 0.15 with the norm being 0.4–4.0 mIU/L and a free T4=79 pmol/L, with the norm 10–27 pmol/L. A TSH of 8.9 again norm 0.4–4.0 mIU/L with a free T4=15 pmol/L, which is within the normal range of 10–27 pmol/L. A TSH of 1.9 with the norm again 0.4–4.0 mIU/L and a free T4=22 pmol/L, with the normal range being 10–27 pmol/L. A TSH 64 with the upper limits of normal of TSH being 4.0 mIU/L and a free T4=3 pmol/L, where the normal range on free T4 is 10–27 pmol/L.
Where do we start with a question like that?
First, we have to determine what type of question is this? This is clearly a diagnosis question. She is a member of the most at-risk gender assignment for this condition, and we're told we're considering a diagnosis of hypothyroidism. She's also in the most common age span for the onset of this condition: ages 30 to 50.
In addition, as is typical with NP board questions, we're really presented with a classic presentation of the disease with increasing fatigue, increased menstrual flow, and dry skin.
Well, it's tempting to skip over this part of the patient narrative as we are asked to simply pick a diagnosis based on the reported labs. Analysis of her symptomatology will really help us to remember the disease's pathophysiology and, of course, pathophysiology invariably leads the way to the correct answer.
Let's take a moment to reflect on what pathophysiology of hypothyroidism is.
The thyroid releases two main hormones, T4 and T3, these are catalysts for generalized cellular energy release and affect literally every cell in the body. With inadequate T3 T4 release, such as seen in thyroid failure, which is part of hypothyroidism, the cells throughout the body release less energy. This can result in fatigue, dry skin, and in women during the reproductive years, increased menstrual flow.
There are, of course, many other signs and symptoms that go along with hypothyroidism. When circulating thyroid hormone levels are low, the anterior low of the pituitary will respond by releasing an increased level of TSH (thyroid-stimulating hormone) to try to boost T4 and T3 levels. Remember, TSH does exactly what the initial stand for: thyroid-stimulating hormone. However, in the failing thyroid, it can't respond appropriately to the increased levels of TSH.
In cases of untreated or newly diagnosed hypothyroidism, TSH levels will be elevated and free T4 levels will be low.
Let's analyze the results provided again.
Again, what we’re gonna do is keep in mind the pathophysiology of hypothyroidism. There is no inadequate levels of thyroid hormones to facilitate cellular energy release and as a result, the interior lobe of the pituitary is going to increase the levels of TSH to try to raise the free T4 levels.
Option A: TSH was low, below 0.15, and the free T4 was markedly elevated at 79, or nearly three times the upper limits of normal. Here we have the elevated free T4 with the result being less than normal TSH produced. Excessive free T4 in circulation produces nervousness, unintended weight loss. Neither reported in this patient. With the lab results such as this coupled with clinical findings, this would be consistent with hyperthyroidism, so obviously is not the correct answer.
Option B: the TSH is 8.9, so it is elevated. It's more than twice the upper limits of normal, but the free T4 is within normal range at 15.
Here we see the TSH is elevated, though not markedly, but the free T4 is within normal limits. In other words, this thyroid needs a little bit extra stimulation to release sufficient amounts of thyroid hormone. This is consistent with subclinical hypothyroidism, a condition that is usually without significant signs or symptoms.
I do want to add, however, that make sure that you are aware of what the current clinical guidelines are for the evaluation and treatment of subclinical hypothyroidism.
Option C: the TSH is 1.9, which is within normal limits and the free T4 is 22, which is also within normal limits. The both values are within normal range, this would be in a bound in a person without thyroid dysfunction and we are being asked specifically in this question to find the results consistent with hypothyroidism.
Option D: the TSH is markedly elevated at 64, with the upper limits of normal being four and the free T4 is three. The lower limits of normal is ten and therefore the amount of circulating thyroid hormone is 30% at very best of what it should be.
At the same time, the anterior lobe of the pituitary is pouring out a lot of TSH, but this poor dysfunctional thyroid, even with all that extra stimulation, cannot produce enough hormone. This is, of course, the correct answer.
Here we see the results of a failing thyroid where even with these markedly elevated TSH levels, but a failing thyroid, even with extra stimulation, cannot produce sufficient T4, which is sometimes called thyroxine.
The result is, of course, this represents hypothyroidism. Key takeaway: when interpreting lab data, keep in mind that the disease's pathophysiology coupled with the clinical presentation, this will help guide you to the right answer.
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.