**Core Concept**
Cyclosporin is an immunosuppressive medication primarily used to prevent transplant rejection and treat autoimmune diseases. Its mechanism of action involves inhibiting calcineurin, a key enzyme in the activation of T-lymphocytes. Cyclosporin's adverse effects are a direct consequence of its immunosuppressive action and its potential impact on various organ systems.

**Why the Correct Answer is Right**
Cyclosporin's adverse effects are mainly due to its nephrotoxicity, neurotoxicity, and hepatotoxicity. The drug can cause vasoconstriction in renal arteries, leading to decreased renal blood flow and glomerular filtration rate. Additionally, cyclosporin can also cause seizures, tremors, and other neurological symptoms due to its neurotoxic effects. Its hepatotoxicity can manifest as elevation of liver enzymes and in severe cases, liver failure.

**Why Each Wrong Option is Incorrect**
**Option A:** Hirsutism is actually an adverse effect of cyclosporin, caused by its effects on the hypothalamic-pituitary-adrenal axis.

**Option B:** Nephrotoxicity is a well-documented adverse effect of cyclosporin, which can lead to chronic kidney disease and end-stage renal failure.

**Option C:** Hyperkalemia is a potential adverse effect of cyclosporin, especially in patients with pre-existing kidney disease.

**Clinical Pearl / High-Yield Fact**
Cyclosporin's nephrotoxicity can be mitigated by co-administering medications that help maintain renal blood flow, such as ACE inhibitors and calcium channel blockers.

**Correct Answer:** D.