POSITIVE THYROTROPIN RECEPTOR ANTIBODIES IN PATIENTS WITH TRANSIENT THYROTOXICOSIS.

POSITIVE THYROTROPIN RECEPTOR ANTIBODIES IN PATIENTS WITH TRANSIENT THYROTOXICOSIS.

Endocr Pract. 2018 Apr 06;:

Authors: Angell TE, Van Benschoten O, Cohen DA, Haas AV, Alexander EK, Marqusee E

Abstract
OBJECTIVE: Thyrotropin (TSH) receptor antibody (TRAb) testing is considered accurate for the diagnosis of Graves' disease (GD), and had been identified rarely in thyrotoxic patients without GD. We describe four patients with transient thyrotoxicosis and positive TRAb to highlight this clinical possibility.
METHODS: Patient demographics, symptoms, laboratory findings, and time to resolution of thyrotoxicosis are summarized. TRAb testing was performed by either a third-generation thyrotropin binding inhibitory immunoglobulin competitive binding assay (TBII) or a thyroid stimulating antibody bioassay (TSI) from either Mayo Clinic Laboratory or Quest Diagnostics.
RESULTS: Four patients with transient thyrotoxicosis and positive TRAb testing were identified. Of these, three were female and median age was 44 years (range 25-49). Median symptom duration at evaluation was 6.5 weeks (range 3-12). No patient had any clinical manifestations unique to GD or had exposure to biotin, thyroid hormone, supplements, iodine, or relevant medications. The TSH was <0.1 mIU/L in all patients. Three patients had a positive TSI, which was elevated less than twice the upper limit of the reference range in all cases, and one patient had a strongly positive TBII. None of the patients were treated with thionamides or RAI. Spontaneous resolution occurred in all patients at a median of 5.5 weeks (range 2-14.4).
CONCLUSION: These cases demonstrate that TSI or TBII may be present in thyrotoxic patients with transient thyrotoxicosis. For clinically stable patients presenting without pathognomonic evidence of GD, mildly elevated TRAb results may require cautious interpretation and alterative diagnostic testing or close monitoring should be considered.
ABBREVIATIONS: ATA = American Thyroid Association; GD = Graves' disease; FT4 = free thyroxine; RAI = Radioactive iodine; RAIU = radioactive iodine uptake; TFT = thyroid function tests; TPO = thyroperoxidase; TRAb = Thyrotropin receptor antibody; TSH = Thyroid stimulating hormone or thyrotropin; TSHR = thyrotropin receptor; TT3 = Total triiodothyronine; TT4 = Total thyroxine; TSI = Thyroid stimulating immunoglobulins; TBII = thyrotropin binding inhibitory immunoglobulin (also known as TBI).

PMID: 29624097 [PubMed - as supplied by publisher]

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