Atrial natriuretic peptide in hypothyroidism

The effect of hypothyroidism on circulating levels of atrial natriuretic peptide (ANP) was studied in 11 hypothyroid patients (aged 11–65 yr; mean, 31 yr) and 13 normal subjects (aged 28–39 yr; mean, 32 yr). Plasma ANP was 32 ± 9 (±sd) pg/ml in normal subjects and 20 ± 5 pg/ml in the hypothyroid patients (P < 0.005). In 7 hypothyroid patients, plasma ANP levels were measured after 10–14 weeks of l-T₄ therapy. ANP increased from 22 ± 5 to 46 ± 18 pg/ml (P < 0.02), along with an increase in mean serum T₄ from 0.6 ± 0.5 to 8.1 ± 2.5 μg/dl (P < 0.001). Thus, hypothyroidism is characterized by decreased circulating levels of ANP which are reversed by l-T₄ therapy.