Final answer:
Chronic constipation in patients with trisomy 21, or Down syndrome, is often caused by hypothyroidism, an endocrine condition where the thyroid gland produces insufficient hormones leading to slowed metabolism and various symptoms including constipation.
Step-by-step explanation:
The endocrine condition that causes chronic constipation in patients with trisomy 21, which is also known as Down syndrome, is hypothyroidism. Hypothyroidism is particularly common in this population. Individuals with trisomy 21 have an increased predisposition to developing hypothyroidism, where the thyroid gland is underactive and does not produce enough thyroid hormones. These hormones are crucial for regulating metabolism, and a deficiency can lead to symptoms such as fatigue, weight gain, and chronic constipation. The treatment for hypothyroidism includes thyroid hormone replacement therapy, which can help alleviate the associated constipation and other symptoms.