Type I renal tubular acidosis is associated with which of the following?

Type I renal tubular acidosis (RTA), also known as distal RTA, is primarily characterized by a defect in the renal tubules' ability to secrete hydrogen ions (H+). This impaired secretion results in a failure to properly acidify the urine, leading to an accumulation of acid in the blood and subsequent metabolic acidosis. In this condition, the inability to excrete H+ effectively results in a low urine pH despite systemic acidosis.

Additionally, patients with Type I RTA may present with hypokalemia due to the increased potassium secretion that often occurs as a compensatory mechanism in response to the metabolic acidosis. However, the hallmark of Type I RTA is primarily the abnormal secretion of hydrogen ions, which is a direct consequence of the dysfunction in the distal tubule.

Hypercalcemia can be seen in some cases, particularly in association with renal stones, but it is not a defining characteristic of Type I RTA itself. Overall, the defining issue in Type I RTA is the abnormal secretion of hydrogen ions leading to metabolic acidosis, which justifies the identification of this condition with abnormal H+ secretion.