Hypothyroidism Diagnosis and Treatment: A Clinical Case Study

History and Physical Findings

The client is a 56-year-old Caucasian female who presents with complaints of fatigue that reportedly began 2 to 3 months prior to her visit. She reports that the fatigue is generalized and constant, and has been progressively worsening since onset. The client reports feeling tired all the time and lacking the energy to perform activities she could normally do, despite sleeping eight hours per night. No relieving factors were identified, although the client reports exertion as a possible aggravating factor. The client is married, has two grown children, and works as a full-time office manager in an internal medicine office. She reports missing a day of work two weeks ago because she "couldn't get out of bed." She denies pain, fever, chills, or recent illnesses, but has gained 5 pounds since her last visit 6 months ago.

The client denies visual changes, ear pain, rhinorrhea, sore throat, or a history of sleep apnea, but reports having had a tonsillectomy as a child. There is no evidence of lymph node tenderness, cough, wheezing, or chest pain, and the client denies nausea, vomiting, diarrhea, and constipation. A review of the skin and endocrine system reveals dry skin and coarse hair, with no evidence of polyuria, polydipsia, or cold intolerance. The client does, however, report worsening depressive symptoms, no suicidal or homicidal thoughts, and generalized muscle weakness with intermittent cramping. The client's past medical history (PMH) includes hypertension, depression, and postmenopausal status, as well as a history of iodine dye allergy and tonsillectomy. She denies cigarette or drug use but admits to consuming 1 to 2 glasses of wine per month. Family history is significant for mental illness, hyperlipidemia, hypertension, and seasonal allergies.

The physical exam shows the client to be alert, oriented, and cooperative, with head, eyes, ears, nose, cardiopulmonary, and abdominal examinations all within normal limits. The client's mood is appropriate and pleasant. The neurological exam shows normal reflexes at the biceps and traceable reflexes at the knees and ankles.

Differential Diagnosis

Three differential diagnoses can be deduced from the subjective and objective information: hyperthyroidism, hypothyroidism, and thyroid cancer. Hyperthyroidism occurs when the thyroid gland overproduces the thyroid hormones T3 and T4, leading to an up-regulation of metabolism that manifests as an increase in heart rate and total body heat production (Dunphy et al., 2019). The clinical presentation includes a combination of anxiety, nervousness, insomnia, weight loss, palpitations, heat intolerance, and fatigue (Dunphy et al., 2019). Patients may also report exertional dyspnea, diarrhea, menstrual irregularities, lower extremity edema, exercise intolerance, musculoskeletal weakness, and weight loss even with increasing appetite (Dunphy et al., 2019).

Hypothyroidism results from the underproduction of thyroid hormones and has the effect of slowing down metabolic processes and many other bodily functions in the same manner as thyroid failure (Dunphy et al., 2019). Risk factors for thyroid failure include radiation treatment, use of iodine or lithium, presence of anti-thyroid antibodies, and a family history of thyroid disease (Dunphy et al., 2019). Fundamental symptoms of hypothyroidism include heavy menses, constipation, cold intolerance, slight weight gain, dry skin, and fatigue (Dunphy et al., 2019). Depending on the duration of illness, the patient may also report very dry skin, hypersomnia, continued weight gain, depression, and mild impairment in mental ability (Dunphy et al., 2019). The primary symptom of thyroid cancer is a painless nodule or lump in the neck, although the patient may also complain of neck tightness, difficulty swallowing, hoarseness, and swollen lymph nodes (Dunphy et al., 2019). Neck pain may also develop depending on the duration of illness (Dunphy et al., 2019).

Thyroid cancer is the least likely diagnosis of the three. The physical exam shows a supple neck devoid of palpable masses, which is the primary characteristic of thyroid cancer. Furthermore, the client denies swollen lymph nodes, difficulty breathing, or any kind of pain, including neck pain. The client's chief complaint is fatigue, coupled with worsening depressive symptoms and musculoskeletal weakness — all of which are characteristic of both hypothyroidism and hyperthyroidism. However, a key identifying symptom of hyperthyroidism is weight loss that persists even with increasing appetite (Dunphy et al., 2019). The client, in contrast, reports continued weight gain and has gained 5 pounds over the past six months. Progressive weight gain is a hallmark of hypothyroidism, making it the most likely diagnosis for this client. Hypothyroidism is the most probable diagnosis, followed by hyperthyroidism, while thyroid cancer is the least likely given the available subjective and objective information.

Diagnostic Testing and Results

Three tests are crucial at this point. First, it is prudent to order thyroid function tests, including the serum TSH test and total free T4 (FT4) to measure circulating T4 levels in the blood (Soh & Aw, 2019). Normal FT4 values range between 0.7 and 1.9 mg/dL, while normal TSH values lie between 0.5 and 5.0 uIU/mL (Samuels et al., 2017). A low FT4 combined with an elevated TSH indicates primary hypothyroidism resulting from disease in the thyroid gland, while a low TSH and low FT4 would be indicative of hypothyroidism due to a problem in the pituitary gland (Samuels et al., 2017). An elevated FT4 with a low TSH indicates hyperthyroidism (Samuels et al., 2017).

In conjunction with thyroid function tests, the clinician should also order a complete blood count (CBC) to exclude anemia or infection as potential causes of the client's depressive symptoms (Lassale et al., 2018). Because low levels of thyroid hormones have been associated with abnormalities in lipid metabolism and increases in total cholesterol levels (Dunphy et al., 2019), it is also prudent to order a lipid panel to assess for hyperlipidemia and to establish baseline values before commencing treatment.

The CBC results show normal levels for all components except an elevated TSH (6.7 uIU/mL) and a low FT4 (0.62 mg/dL), which are indicative of primary hypothyroidism resulting from disease in the thyroid gland (Samuels et al., 2017). The CBC results rule out anemia or infection and suggest that the client's depressive symptoms are likely related to her thyroid condition. The client reports a depression score of 10 on the PHQ-9 scale, a 5-point increase from her score during the last visit 6 months ago.

References

FDA. (2017). LEVO-T: Highlights of prescribing information. Food and Drug Administration. Retrieved from https://www.accessdata.fda.gov/drugsatfda_docs/label/2017/021342s023lbl.pdf

Lassale, C., Curtis, A., Abete, I., Van der Schouw, Y., Verschuren, M., Lu, Y., & Mesquita, B. (2018). Elements of the complete blood count associated with cardiovascular disease incidence: Findings from the EPIC-NL cohort study. Scientific Reports, 8(1). doi:10.1038/s41598-018-21661-x

Samuels, M. H., Kolobova, I., Antosik, M., Niederhausen, M., Purnell, J., & Schuff, K. (2017). Thyroid function variation in the normal range, energy expenditure, and body composition in L-T4 treated subjects. Journal of Clinical Endocrinology & Metabolism, 102(7), 2533–2542.

Soh, S., & Aw, T. (2019). Laboratory testing in thyroid conditions — pitfalls and clinical utility. Annals of Laboratory Medicine, 39(1), 3–14.

Dunphy, L. M., Winland-Brown, J. E., Porter, B. O., & Thomas, D. J. (2019). Primary care: The art and science of advanced practice nursing (5th ed.). F.A. Davis Company.