Thyrotoxicosis factitia is a rare disorder characterized by elevated levels of plasma thyroid hormones due to increased intake which can be iatrogenic, accidental, or intentional. Symptoms are similar to those in Grave's disease and diagnosis is based on history, examination findings, and by testing thyroid functions.
Thyrotoxicosis factitia (TF) is also known as thyroxine addict or metabolic malingerer [1] [2] syndrome. It occurs in patients who are prescribed a very high dose of thyroid hormones as medication (iatrogenic); or those who consume thyroid hormone medication surreptitiously for weight loss or to increase their energy levels or to decrease sleep but deny taking the medication (intentional); or in children (accidental) or adults who consume meat containing thyroid tissue (accidental).
Clinical presentation of TF is identical to thyrotoxicosis except that patients with TF do not have a goiter (thyromegaly) and unlike patients with Grave's disease, they have neither exophthalmos nor myxedema (thickened skin over their shins). Features of thyrotoxicosis like anxiety, hyperactivity, increased perspiration, dyspnea, intolerance to heat, unexplained weight loss, diarrhea, fine tremors, hyperreflexia, tremulousness, palpitations and atrial fibrillation are seen in TF too. Complications like cardiac arrhythmias, hypermetabolism, hyperpyrexia, thyroid storm and myocardial infarction have been reported in TF [3] [4].
The initial diagnosis of TF is based on clinical suspicion. A detailed history is essential to determine medicine intake, diet, the degree of symptom progression and underlying psychiatric issues. Physical examination should take into consideration the patient's heart rate, basal metabolic rate, presence or absence of goiter, exophthalmos, and myxedema. Laboratory biochemical tests are required to determine total triiodothyronine (T3), total thyroxine (T4), thyroid-stimulating hormone (TSH), TSH receptor, and thyroglobulin level. An elevated free thyroxine index (ratio of T-4 to T-3) [5], diminished thyroglobulin level [6] with an increased basal metabolic rate are diagnostic of TF. Patients with a positive TSH receptor and hyperthyroidism can be misdiagnosed as Grave's disease [7]. To distinguish TF from other causes of thyrotoxicosis, fecal thyroxine levels can be obtained with elevated levels confirming the diagnosis of TF [8].
An imaging study like color doppler ultrasonography is also useful to diagnose TF as it demonstrates the lack of thyroid blood flow [9]. If a patient has an elevated free thyroid hormone level with low TSH levels but is not able to provide a history of ingesting thyroid hormones, a radioactive iodine I-123 uptake is indicated and a low uptake is suggestive of TF [10].
A psychiatrist referral must be considered to exclude Munchausen syndrome [11] and other psychiatric disorders.