Which of the following is NOT a characteristic of cystic fibrosis?

Cystic fibrosis is a genetic disorder that primarily affects the respiratory and digestive systems due to mutations in the CFTR gene. The most notable characteristics of cystic fibrosis include chronic respiratory infections, pancreatic insufficiency, and thick mucus production.

Chronic respiratory infections arise because the thick, sticky mucus obstructs the airways, making it difficult to clear bacteria and debris. The lungs become an environment ripe for infections, leading to recurrent respiratory issues.

Pancreatic insufficiency occurs because the thick mucus can block the pancreatic ducts, leading to a reduced ability to secrete digestive enzymes necessary for the absorption of nutrients. This results in malnutrition and difficulties in digesting food.

Thick mucus production is a hallmark feature of cystic fibrosis, caused by the malfunction of the CFTR protein, which regulates the movement of chloride and sodium ions across epithelial cells, leading to overly viscous secretions.

In contrast, increased tyrosine production is not a characteristic of the condition. The disorders associated with cystic fibrosis do not involve abnormalities in amino acid metabolism or an increase in tyrosine levels, making this option factual because tyrosine metabolism is not directly related to the pathophysiology of cystic fibrosis.