**Core Concept**
Morbid jealousy is a psychiatric disorder characterized by an excessive and irrational preoccupation with the idea that one's partner is unfaithful. It is a form of delusional disorder that can cause significant distress and impairment in social and occupational functioning.

**Why the Correct Answer is Right**
The correct answer involves the involvement of the neurotransmitter serotonin in the regulation of mood and emotional responses. Individuals with morbid jealousy often have an imbalance in serotonin levels, which can contribute to the development of the disorder. Additionally, the condition is often associated with underlying personality disorders, particularly borderline personality disorder.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because morbid jealousy is not directly related to the use of anabolic steroids, which are primarily used to enhance athletic performance.
**Option B:** This option is incorrect because paranoid personality disorder is a distinct personality disorder characterized by a pervasive distrust and suspiciousness of others, but it is not directly associated with morbid jealousy.
**Option C:** This option is incorrect because obsessive-compulsive disorder (OCD) is a separate psychiatric condition characterized by recurring, intrusive thoughts and compulsions to perform specific rituals or behaviors, but it is not directly related to morbid jealousy.

**Clinical Pearl / High-Yield Fact**
Morbid jealousy often presents with a characteristic pattern of behavior, including excessive questioning, spying, and accusations of infidelity. Physicians should be aware of this presentation and consider psychiatric evaluation if a patient's partner reports such behavior.

**Correct Answer:** D. Othello syndrome, also known as morbid jealousy, is a type of delusional disorder.