Juvenile Idiopathic Arthritis (JIA): Given the long-standing history of bone and joint pain since the age of eight, JIA is a strong consideration. The elevated alkaline phosphatase and low vitamin D levels could be related to chronic inflammation and decreased mobility, which are common in JIA.

Vitamin D Deficiency: The low vitamin D level (14) could be contributing to the bone and joint pain, and it's essential to address this deficiency. Vitamin D deficiency can lead to osteomalacia or rickets in adolescents, which would explain the elevated alkaline phosphatase.
Hypothyroidism: Although not directly indicated by the provided lab values, hypothyroidism can cause joint pain, elevated prolactin levels, and alterations in vitamin D and calcium metabolism. It's a common condition that can present with non-specific symptoms.
Fibromyalgia: This condition is characterized by widespread musculoskeletal pain and could be a consideration, especially if other diagnoses are ruled out. However, the laboratory abnormalities would need to be explained by another condition.

Hyperparathyroidism: Although the calcium level is within the normal range, hyperparathyroidism can cause bone and joint pain, elevated alkaline phosphatase, and alterations in vitamin D levels. It's crucial to rule out this condition due to its potential for significant morbidity if left untreated.
Malignancy (e.g., Leukemia, Lymphoma): Bone and joint pain can be a presenting symptom of various malignancies. Although less likely, it's critical to consider and rule out these conditions due to their severe prognosis if missed.
Osteogenesis Imperfecta: A genetic disorder that affects the production of collagen, leading to bone fragility and pain. The elevated alkaline phosphatase could be indicative of bone turnover.

McCune-Albright Syndrome: A rare genetic disorder characterized by fibrous dysplasia of bone, café-au-lait spots, and various endocrine disorders, including hyperprolactinemia. The combination of bone pain, elevated prolactin, and low vitamin D could suggest this diagnosis, although it is rare.
Gaucher's Disease: A lysosomal storage disorder that can cause bone pain, joint pain, and elevated alkaline phosphatase due to bone marrow infiltration. It's a rare condition but should be considered in the differential diagnosis due to its potential for significant morbidity.