Thyrotoxicosis is the presentation with symptoms, signs, and/or labs pointing to elevated thyroid hormone level (1). This can be due to excessive thyroid hormone production by an overactive thyroid (i.e., hyperthyroidism) or to the thyrotoxic phase of thyroiditis among less frequent etiologies (1). Hyperthyroidism can be due to Graves’ disease, toxic thyroid adenoma, toxic multinodular goiter, or amiodarone-induced thyroiditis type 1 (2). The toxic phase of thyroiditis can happen due to subacute thyroiditis, post-partum thyroiditis, or amiodarone-induced thyroiditis type 2. Clinical assessments, including history, physical exam, and labs, are essential. Thyroid scan and uptake studies are also frequently utilized to confirm the diagnosis (3).

Identifying the underlying reason for thyrotoxicosis is crucial as it will guide therapy, which can vary widely based on the etiology outside of the realm of just symptomatic therapy, like beta-blockade. For instance, Graves’ disease can be treated by thioamides like methimazole, moderate to severe subacute thyroiditis by prednisone, and mild postpartum thyroiditis by reassurance (3). History and physical exam findings are critical as different diseases frequently have different presentations. The commonly used tools to confirm the diagnosis include measuring the specific antibodies for Graves’ disease, like thyroid stimulating immunoglobulin (TSI) and thyroid scan and uptake (3).

Certain diseases can make the diagnostic work-up challenging. For example, in postpartum thyroiditis for nursing women, it is recommended to avoid exposure to radioactive iodine as it will be expressed in the breast milk (4). In amiodarone-induced thyroiditis, the patients have a high iodine load in their bodies, and therefore, the thyroid scan and uptake usually show low uptake (5). Also, the antibody elevation is inconsistent in both types (6). It is also important to screen such patients for thyroid nodules. Of note, there is a higher likelihood of cancer in patients with Graves’ disease, possibly due to the high stimulatory antibody titers (7). On the other hand, the risk of cancer in toxic nodules is lower, so the need for biopsy is much less (8). Therefore, a screening ultrasound is also a necessity.

The medication management of patients with Graves’ disease differs from those with toxic adenoma and toxic multinodular goiter (3). For example, the dosing approach for thionamides differs amongst the different disease processes. Per the principal investigator’s experience, those with Graves’ disease will usually start off with a loading dose and then complete a rapid taper, but patients with toxic adenoma or toxic multinodular goiter will have a relatively steadier dosing regimen. Additionally, steroid therapy in patients with moderate to severe subacute thyroiditis is often necessary (9). To avoid unnecessary medication side effects and hazards, establishing the correct diagnosis upfront is paramount.

Point-of-care ultrasound (POCUS) is widely available and is becoming the standard of care in many endocrinology practices, especially thyroid-focused ones. There’s an evolving body of evidence to support the utility of Spectral Doppler Ultrasound (SDUS) in determining the diagnosis in patients presenting with thyrotoxicosis, often during the initial clinical encounter (10). It’s a bedside tool shown to help differentiate etiologies of thyrotoxicosis. In addition, thyroid nodules can be easily screened for during the same exam, making it an efficient and multipurpose screening tool for patients.

In Graves’ disease, highly suggestive physical exam signs include a palpable thrill and an audible bruit (11). Both point to the significantly increased speed of thyroidal vascular flow. SDUS will quantify this finding and measure the actual velocity. In thyroiditis, the blood flow rate varies based on its stage, ranging from very high to low vascularity, and occasionally, thyroid inferno will be demonstrated on Doppler ultrasound in the early phase of the disease (12). Yet, the velocity of blood flow is lower than Graves’ disease. Understandably, each disease has its spectrum of severity, so there is an expected overlap. The thyroid scan and uptake is an important tool and helpful in controversial cases. However, it is more expensive, doesn’t provide detailed anatomical findings, and carries hazards of mild radiation exposure as compared to a thyroid ultrasound (13).

In this retrospective study, we are assessing the utility of SDUS in the initial assessment of patients presenting to a thyroid-focused academic endocrinology clinic for evaluation and management of thyrotoxicosis. This includes the accuracy of diagnosis by the end of the initial clinical encounter, sensitivity and specificity, and screening for thyroid nodules in these patients.