Table 2. A 19-year-old female with pseudohyperthyroidism due to self-prescribed 20 mg/day biotin for hair and nail changes in iron deficiency anemia and polycystic ovary syndrome.

Investigations	Initial investigations Aug 30, 2018	On biotin		Off biotin			Normal values
		Nov 22, 2018	Nov 24, 2018	24 hours after	48 hours after	72 hours after
TSH µIU/ml	0.86	0.04	0.05	1.04	1.11		0.27-4.2
FT4 ng/dl	1.63	3.23	3.48	2.55	2.30	1.04	0.93-1.7
FT3 pg/ml			4.01	2.24			1.21-4.18
TT4 µg/dl	14.00	22.12	20.17	10.30			5.1-14.1
TT3 ng/ml	0.9	4.21	4.56	1.56			0.8-2
Anti-TPO IU/ml			3.22				0-34
TRAb mIU/ml			0.68				<2
¶ Roche Cobas e411 immunoassay. TSH: Thyroid-Stimulating Hormone, FT4: Free Thyroxine, FT3: Free Triiodothyronine, TT4: Total Thyroxine, TT3: Total triiodothyronine, Anti-TPO: Antithyroid Peroxidase, TRAb: Thyrotropin Receptor Antibody.