Based on prior knowledge, it is difficult to determine the relationship between the feature "endocr_03" and the target variable "chronic heart failure" without additional information. Thyrotoxicosis in the anamnesis (history of thyroid disorder) may or may not indicate a chronic heart failure. To proceed with the analysis, we need more context or data on the relationship between endocr_03 and chronic heart failure.

However, based on the available information, we can create a dictionary in the desired format. Since we don't have any specific information about the relationship between the feature and the target, we can only include the possible values of "endocr_03" for each target class:

```json
{
    "no": ["no"],
    "yes": ["no", "yes"]
}
```

This dictionary indicates that for the target class "no" (no chronic heart failure), the only possible value for "endocr_03" is "no." For the target class "yes" (chronic heart failure), both "no" and "yes" values are possible for "endocr_03".