**Core Concept**
Parenteral iron therapy is a method of administering iron directly into the bloodstream, bypassing the gastrointestinal tract. It is used in cases where oral iron supplementation is ineffective or not feasible due to various reasons such as chronic blood loss, malabsorption, or intolerance.

**Why the Correct Answer is Right**
The correct answer involves identifying the scenario where parenteral iron therapy is the preferred choice. Parenteral iron therapy is indicated when there is a significant iron deficiency or iron deficiency anemia that cannot be corrected with oral iron supplements. This can occur in cases of chronic blood loss, such as in patients with gastrointestinal bleeding, menstruating women with heavy menstrual bleeding, or those with chronic kidney disease. In these situations, the body's iron stores are depleted, and oral iron supplementation is insufficient to replenish them.

**Why Each Wrong Option is Incorrect**
**Option A:** This option may be tempting, but parenteral iron therapy is not solely indicated for patients with iron deficiency anemia without any underlying cause. Oral iron supplements are usually the first line of treatment for iron deficiency anemia.

**Option B:** This option is incorrect because parenteral iron therapy can be used in cases of iron deficiency anemia due to chronic blood loss, not just in patients with gastrointestinal bleeding. Other causes of chronic blood loss, such as menstruating women or those with chronic kidney disease, also require parenteral iron therapy.

**Option C:** This option is not entirely incorrect, but it is too broad. Parenteral iron therapy is indeed used in patients with chronic kidney disease, but it is not the only indication. Other conditions, such as gastrointestinal bleeding, also require parenteral iron therapy.

**Option D:** This option is incorrect because parenteral iron therapy is not solely indicated for patients with iron overload. In fact, parenteral iron therapy is used to treat iron deficiency, not iron overload.

**Clinical Pearl / High-Yield Fact**
When considering parenteral iron therapy, it is essential to evaluate the underlying cause of iron deficiency anemia and assess the patient's overall iron status before initiating treatment.

**Correct Answer:** C.