Category: Thyroid

Monitor: 34

34 - ISOLATED FREE T3 THYROTOXICOSIS: FACT OR FICTION ?

Friday, Apr 26
12:00 PM – 12:30 PM

Objective : Thyrotoxicosis Factitia (TF) could be very difficult to establish. We report an interesting case of isolated T3 thyrotoxicosis due to surreptitious ingestion.


Methods : Case Report and literature review


Results : A 57-year-old female was referred to our clinic for evaluation of abnormal Thyroid function tests(TFT’s). She reported an unintentional 40-pound weight loss along with complaints of episodic palpitations, tremors, diaphoresis and fatigue. Extensive review of system was negative, including ingestion of any thyroid supplements, herbal supplements or other potential medications associated with thyrotoxicosis. TSH level was <0.01(ref: 0.45-4.6 mU/L) and FT4 level was 0.1(ref: 0.8-1.7 ng/dL). FT3 levels were 13.3(ref: 2.0-4.8 pg/ml).Repeat TFT’s demonstrated suppressed TSH and FT4 levels and elevated FT3 levels (TSH: <0.01, FT4: 0.1; FT3: 13.5). Radioactive Iodine-Uptake(RAIU) showed a 6-hour uptake of 2% and 24-hour uptake of 3%). Serum Thyroglobulin(TG) level was 3 ng/ml with TGAb level of  <20 IU/ml. Serial TFT’s showed suppressed TSH and FT4 with elevated FT3 levels despite up-titration of Methimazole and short term use of prednisone. Ultrasound Pelvis did not show any evidence of Ovarian or Pelvic mass. Methimazole was discontinued given no discernible benefit. Her serial TFT’s have consistently shown suppressed TSH and FT4 with somewhat variable(but high) FT3 levels. Patient continues to deny any exogenous thyroid supplement/medication use. After extensive intra-departmental discussion, we have decided that the current clinical evidence points towards TF and no further work-up or anti-Thyroidal drug management will be pursued.


Discussion : Endogenous isolated FT3 thyrotoxicosis has been reported in few cases of Toxic nodules and Graves’ disease. There also have been case reports of isolated Free T3 thyrotoxicosis complicating Metastatic Follicular Thyroid Carcinoma and Multiple Myeloma. However, more common scenario for T3 thyrotoxicosis would be exogenous intake(either surreptitious or accidental). Unfortunately, there is no easy way to diagnose surreptitious use and one needs to have a high degree of clinical suspicion for TF. Some clues towards exogenous T3 ingestion could be low RAIU, suppressed TG and FT4 levels. Per our review of the available literature, no cases with endogenous FT3 thyrotoxicosis have been reported  with completely suppressed FT4 levels or low thyroglobulin levels.


Conclusion : Our case highlights challenges associated in determining TF and one needs to have a high degree of clinical suspicion for the same in order to avoid a time consuming and expensive medical work-up.

Dinkar Rupakula

Endocrinology Fellow
University of Arizona
Oro Valley, Arizona

Endocrinology Fellow, University of Arizona

Juan Galvez

Assistant Professor
University of Arizona

Assistant Professor, Medicine
Associate Program Director, Endocrinology, Diabetes and Metabolism Fellowship