A 42-year-old florist presents with chronic constipation and fatigue. What endocrine disorder could be contributing to her symptoms?

Hypothyroidism can significantly contribute to symptoms such as chronic constipation and fatigue, making it the most relevant endocrine disorder in this scenario. In hypothyroidism, the metabolism slows down due to insufficient thyroid hormone production, which can lead to a decreased motility of the gastrointestinal tract, resulting in constipation. Additionally, individuals with hypothyroidism often experience fatigue due to the body's slowed metabolic processes and reduced energy levels.

The other options present endocrine disorders that may not commonly align with both symptoms presented. For instance, diabetes mellitus typically involves symptoms related to blood sugar regulation, such as increased thirst and frequent urination, rather than constipation and fatigue as primary complaints. Cushing's syndrome might lead to fatigue but is more associated with weight gain, changes in appearance, and potential glucose intolerance. Hyperthyroidism would usually present with symptoms such as increased bowel movements, weight loss, and increased energy, contrasting with the chronic constipation experienced by the patient. Thus, given the symptoms, hypothyroidism emerges as the most fitting endocrine disorder related to her condition.