Morbidity in patients on L-thyroxine: a comparison of those with a normal TSH to those with a suppressed TSH.
OBJECTIVE
Patients on L-thyroxine with a 'suppressed' TSH (< 0.05 mU/l) were compared to those in whom TSH was detectable but not elevated (0.05-4.0 mU/l), with regard to morbidity data.


METHODS
Biochemical data from Tayside Thyroid Register was matched to hospital admissions data obtained from Health Board Statistics.


METHODS
The patients were identified from those registered on the computerized Tayside Register.


METHODS
Serum T4 and TSH assays, clinical assessment scores, and admission records with regard to ischaemic heart disease, overall fractures, fractured neck of femur and breast carcinoma.


RESULTS
Over one year, 1180 patients on thyroxine replacement had clinical and biochemical assessment; 59% had a suppressed TSH and 38% 'normal' TSH. Patients with a suppressed TSH exhibited higher median serum thyroxine levels (146 nmol/l, range 77-252 vs 119 nmol/l, 58-224; P < 0.001). Patients under the age of 65 years on L-thyroxine had an increased risk of ischaemic heart disease compared to the general population (female 2.7 vs 0.7%, P < 0.001; male 6.4 vs 1.7%, P < 0.01), but the risk was no different between those with suppressed and normal TSH. There was no increase in risk for overall fracture, fractured neck of femur or breast carcinoma in those on thyroxine with suppressed or normal TSH.


CONCLUSIONS
Patients under the age of 65 years on L-thyroxine had an increased risk of ischaemic heart disease. There was no excess of fractures in patients on L-thyroxine even if the TSH is suppressed.
Leese
G P
GP
University Department of Medicine, Ninewells Hospital and Medical School, Dundee, Scotland.
Jung
R T
RT
Guthrie
C
C
Waugh
N
N
Browning
M C
MC
D000368:Aged; D001943:Breast Neoplasms / Q000209:etiology; D003864:Depression, Chemical; D005260:Female; D005265:Femoral Neck Fractures / Q000209:etiology; D005500:Follow-Up Studies; D050723:Fractures, Bone / Q000209:etiology; D006801:Humans; D007037:Hypothyroidism / Q000097:blood / Q000188:drug therapy / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D017202:Myocardial Ischemia / Q000209:etiology*; D012307:Risk Factors; D013972:Thyrotropin / Q000097:blood / Q000378:metabolism*; D013974:Thyroxine / Q000009:adverse effects* / Q000627:therapeutic use
D013972:Thyrotropin; D013974:Thyroxine