Functional Constipation: This is the most common cause of constipation, often related to diet, lifestyle, and bowel habits. It is characterized by infrequent bowel movements, hard stools, and difficulty passing stools without an underlying medical condition.

Hypothyroidism: Constipation is a common symptom of hypothyroidism due to decreased metabolic rate affecting bowel motility.
Medication Side Effects: Many medications, such as opioids, anticholinergics, and iron supplements, can cause constipation as a side effect.
Dietary Factors: Low fiber intake, inadequate fluid consumption, and a diet high in processed foods can contribute to constipation.
Physical Inactivity: Sedentary lifestyle can reduce bowel motility and contribute to constipation.

Colorectal Cancer: Although less common, colorectal cancer can present with constipation, especially if there is a significant change in bowel habits.
Intestinal Obstruction: Partial or complete blockage of the intestine can cause severe constipation and is a medical emergency.
Neurological Disorders: Conditions like Parkinson's disease, multiple sclerosis, and spinal cord injuries can affect bowel function and cause constipation.
Endocrine Disorders: Besides hypothyroidism, other endocrine disorders like hyperparathyroidism and diabetes mellitus can also lead to constipation.

Hirschsprung's Disease: A congenital condition characterized by the absence of ganglion cells in the distal bowel, leading to severe constipation.
Chagas Disease: Caused by the parasite Trypanosoma cruzi, it can lead to megacolon and constipation in its chronic phase.
Amyloidosis: A condition where abnormal proteins (amyloid) accumulate in various organs, including the gastrointestinal tract, potentially causing constipation.
Scleroderma: A chronic autoimmune disease that can affect the gastrointestinal tract, leading to constipation among other symptoms.