Alterations of carboxypeptidases N activities in patients with thyroid dysfunction.

Serum carboxypeptidases N (EC. 3.4.17.3) were determined spectrophotometrically in 87 patients with disturbances of thyroid function and in 131 euthyroid individuals, including 33 women taking estrogens for contraception. Carboxypeptidases N (CN) can be subdivided into CN1 and CN2, according to variable substrate affinity. In addition, measurements of blood pressure and in vitro tests of thyroid function were performed. In euthyroid controls, CN1 was negatively correlated with age. No significant differences between CN1 and CN2 have been observed with regard to sex. In patients with hyperthyroidism, the mean values of both enzymes were elevated, but this tendency proved to be significant only for CN2. In hypothyroid patients CN1 and CN2 levels were normal. Elevations of CN1 and CN2 in the hyperthyroid state seem not to be related to underlying immunological processes but to the thyroid hormone excess itself. In euthyroid women taking estrogens for contraception CN2 was also elevated.

PIP: The serum enzymes called carboxypeptidase N that split arginine or lysine from certain peptides, here termed CN1 and CN2, were determined in patients with thyroid disorders and in women taking oral contraceptives. The assays were done spectrophotometrically using synthetic hippuryl-substrates. The normal ranges in euthyroid subjects were 13-49 Units/1 for CN1 and 71-181 for CN2. In normal subjects, CN1 was inversely correlated with age. In hyperthyroid patients, the levels of both enzymes were elevated, significant only for CN2. Mean CN2 was significantly elevated in 33 women taking oral contraceptives, compared to euthyroid controls, 148.6 u/1, but was not outside the normal range.

Changes of serum angiotensin-I-converting enzyme in patients with thyroid disorders.

In 149 subjects (63 euthyroid, 21 hyperthyroid, 26 with autonomous nodules, subdivided into 20 euthyroid and 6 hyperthyroid, 17 hypothyroid subjects and 22 women taking estrogens) the serum angiotensin-I-converting enzyme (SACE) was spectrophotometrically measured and correlated with age, systolic and diastolic blood pressure, free thyroid hormones (FT4, FT3) and delta TSH level. In patients with diffuse hyperthyroidism and with regional autonomy, systolic blood pressure was elevated. The highest values for FT4 and FT3 were found in patients with hyperthyroidism and hyperthyroid autonomous nodules. SACE correlated with age for the euthyroid control group (p less than 0.05). In this group, SACE levels were higher in men than in women (p less than 0.02). Regarding all 149 subjects together, significant linear correlations between SACE and systolic blood pressure as well as with FT4 and FT3 concentrations could be demonstrated (p less than 0.01-0.001). Among the individual groups the mean SACE activities were significantly elevated in hyperthyroid patients (p less than 0.01). No significant differences could be observed between controls and euthyroid subjects with autonomous nodules as well as in hypothyroid cases. In comparison to euthyroid patients the mean SACE levels of hyperthyroid patients with autonomy were significantly (p less than 0.05) elevated. The SACE activities of women taking estrogens for contraception did not differ significantly from SACE in age-matched female controls.