Summary
Serum angiotensin converting enzyme activities were significantly increased in 26
untreated hyperthyroid patients (20.3 ± 5.4 U/ml; P < 0.001) compared with healthy
control subjects (13.1 ± 2.3 U/ml). In 12 patients a significant fall in enzyme activities
was observed after treatment compared with pretreatment serum ACE levels (P < 0.001).
Eight patients with hypothyroidism (15.7 ± 5.1 U/ml) and 11 arthyreotic patients,
totally thyroidectomized for well-differentiated thyroid cancer, showed no significant
differences in serum ACE activities (14.3 ± 2.2 U/ml) compared with control subjects.
After thyroid hormone supplementation a significant increase in serum ACE activity
(P < 0.05) was found in the athyreotic patients. Addition of increasing amounts of
L-thyroxine to a serum sample of an athyreotic patient showed no significant effect
on ACE activity in vitro. We suggest that the elevated serum ACE activity in hyper-thyroidism
is not from the thyroid gland, but represents a direct effect of thyroid hormone on
ACE synthesis and/or release from endothelial cells.
Key-Words:
Angiotensin-Converting Enzyme
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Thyroid Gland
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Hyperthyroidism
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Hypothyroidism
