This work studies the thyroid disorders impact on adrenals glands by measuring total cortisol. Radioimmunoassays of thyroid hormones and cortisol were performed in 108 subjects, aged 20-52 years, with thyroid diseases. Our results show low cortisol values (80.35 nmol/L) in 4.77% of hyperthyroids, high values in 3.57% of hyperthyroids (1348.18 nmol/L) and 12.5% of hypothyroids (969.05 nmol/L). In hyperthyroidism, thyroid hormone stimulates the secretion of 11 ceto metabolites biologically inactive, unable to slow pituitary activity, inducing an increased production of endogene cortisol. Excessive catabolism can lead to the exhausting of overstimulated adrenal glands, and therefore to a decreased cortisol. In hypothyroidism, high cortisol results of increase cortisol half life and decrease of metabolic clearance. Control mechanisms often allow normal cortisol values. These alterations in functional activity of adrenal glands, seen in nearly 10% of these subjects, sometimes command a specific attitude in diagnosis and therapy.