The clinical observation of a series of 30 patients (age 29.6 +/- 9.8 years, 29 females and 1 male) who were remitted for evaluation of a thyroid dysfunction with a decrease in TSH and free thyroxin with clinical symptoms of hyperthyroidism and absence of goiter or exophthalmous is presented. Most of the patients (90%) had no family or personal history of previous thyroid disease. Anamnesis demonstrated the previous ingestion of uncommercialized prepared weight losers, dispensed in different areas off the pharmacy offices. Seventy-three percent of the patients had received the treatment from the same source (prescriber). In most of the cases (28 out of 30) normalization was observed in thyroid function tests. The demonstrated inefficacy of this medication as well as the health care importance of the problem are discussed.