Which of the following is not a steroid hormone?

Options

A. Androgen
B. Aldosterone
C. Estrogen
D. Relaxin

Answer

To determine which of the following is not a steroid hormone, we need to analyze the options provided: Androgen, Aldosterone, Estrogen, and Relaxin.

### Step-by-Step Solution:

1. **Understand the Types of Hormones**: Hormones can be classified based on their chemical structure. The main categories include steroid hormones, peptide hormones, and amino acid derivatives.

2. **Identify Steroid Hormones**:
- **Androgens**: These are steroid hormones that include testosterone and are involved in male traits and reproductive activity.
- **Aldosterone**: This is a steroid hormone produced by the adrenal glands that helps regulate sodium and potassium levels in the body.
- **Estrogen**: This is also a steroid hormone, primarily involved in the regulation of the female reproductive system.

3. **Analyze the Fourth Option - Relaxin**: Relaxin is a hormone that is secreted by the ovaries during pregnancy. It is primarily involved in the relaxation of the pelvic ligaments and the cervix during childbirth.

4. **Determine the Chemical Nature of Relaxin**: Unlike the other three hormones listed, Relaxin is not classified as a steroid hormone. It is a peptide hormone, which means it is made up of amino acids.

5. **Conclusion**: Since Relaxin is not a steroid hormone, the correct answer to the question is **Relaxin**.

### Final Answer:
The hormone that is not a steroid hormone is **Relaxin**.

---