Case History: A 26 year old female patient was referred to her local endocrine clinic having presented to her GP complaining of ankle swelling. Routine biochemistry revealed a suppressed TSH (<0.05 U/l), and reduced serum levels of free T4 (2.0 pmol/l) and T3 (3.2 pmol/l). Random serum cortisol measurements were also elevated on 2 separate occasions (1266 nmol/l and 991 nmol/l). Clinical examination revealed her to be clinically euthyroid with no evidence of glucocorticoid excess, and no visual field defect was noted.
Investigations: The patient had normal 24 hour urinary steroid profile, and 8am cortisol suppressed to 42 nmol/l during an overnight dexamethasone suppression test. Serum prolactin and GH were also within the normal reference ranges. LH and FSH were fully suppressed as the patient was taking a combined oral contraceptive pill. MRI pituitary was reported as normal.
Results and Treatment: A diagnosis of secondary hypothyroidism was made. Levothyroxine was commenced at a dose of 50 mcg daily. The patient was reviewed after 8 weeks, and FT4 was within the normal range at 12.2 pmol/l, with TSH remaining suppressed. The patient was reviewed 4 months later, by which point she was complaining of heat intolerance and hair loss. Thyroid biochemistry was as follows: TSH <0.05, FT4 8.4 pmol/l, T3 44.0 pmol/l. On further questioning, it became apparent that the patient had been regularly ingesting a number of supplements to aid weight loss.
Conclusions: This case illustrates the potential for inadvertent thyroid hormone ingestion, in patients using energy and weight loss supplements. In this case, regular ingestion of T3 may have led to a biochemical picture mimicking secondary hypothyroidism.