Iatrogenicity is inherent to endocrinology, being a consequence of treatment (e.g., use of thyroid hormones in large doses to suppress thyroid stimulating hormone [TSH] in thyroid cancer) or occurring due to a lack of patient compliance (e.g., lack of adequate controls in chronic diseases, such as Hashimoto’s chronic thyroiditis). Quite often, it is induced as a side effect of medicines (e.g., long-lasting use of antithyroid agents or glucocorticoids). In this chapter, we review the most important iatrogenic effects, according to the main features of endocrinology. We present certain drugs that can trigger particular syndromes, such as the syndrome of inappropriate antidiuretic hormone secretion (SIAHS), along with preparations with pitressin and complications of treatment performed for pituitary adenomas, potential complications of drugs used to treat pituitary insufficiency in children and other specific features constituting required knowledge for medical practitioners. All therapeutic modalities of hyperthyroidism (medical, surgical, radioiodine) can cause iatrogenic pathology. For example, the euthyroid state is a sine qua non condition of thyroid surgery (except the thyrotoxic storm in advanced stages). Radioiodine treatment, in turn, has its own contraindications. Iodine-containing preparations can activate thyroid autonomies and aggravate autoimmune thyroiditis and overt hyperthyroidism. In hypothyroid elderly and cardiac patients, the thyroid hormone substitution must be applied only after initial cardiovascular treatment, in small, gradually increasing doses. In Addison’s disease, indication of dietary salt reduction alongside glucocorticoid substitution, or the lack of increase in glucocorticoid dose in acute injuries, are serious iatrogenic complications.