Comprehensive Osteopathic Medical Licensing Examination (COMLEX) Level 3 Practice Test

The symptoms of diarrhea, skin changes, and hair loss are consistent with a deficiency in zinc. Zinc is an essential trace element that plays a vital role in numerous biological functions, including immune response, protein synthesis, wound healing, and DNA synthesis.

Diarrhea can occur in zinc deficiency due to impaired gut function and mucosal integrity. The skin changes, often manifested as dermatitis or rashes, relate to zinc's role in skin health and repair, as well as its involvement in the maintenance of proper cell membrane integrity. Hair loss can also result from zinc deficiency, as zinc is important for hair follicle function and overall hair health.

Additionally, while iron deficiencies can lead to symptoms like fatigue and weakness, they are less directly associated with skin and hair manifestations. Vitamin C deficiency leads to scurvy, characterized by bleeding gums and bruising, whereas biotin deficiency primarily presents with brittle hair and skin rashes, but not typically with diarrhea. Thus, the combination of diarrhea, skin changes, and hair loss distinctly points to zinc deficiency as the correct answer.