**Question:** Which of the following cause early onset of rigor mortis?

A. Hypothermia
B. Hypoxia
C. Hypoglycemia
D. Hypokalemia

**Core Concept:**
Rigor mortis is a series of post-mortem changes in muscle tone, stiffness, and rigidity that occur as a result of muscle-cell death, energy depletion, and muscle enzyme inactivation. The onset of rigor mortis depends on factors affecting the rate at which these processes occur.

**Why the Correct Answer is Right:**
Correct Answer: Hypothermia (C) causes early onset of rigor mortis. Hypothermia leads to a reduction in cellular activity and slows down the post-mortem enzymatic processes. This results in a delay in the onset of rigor mortis, as the muscle enzymes have less time to inactivate and cause muscle rigidity.

**Why Each Wrong Option is Incorrect:**
A. Hypoxia (B) does not directly affect the rate of muscle enzyme inactivation, which is the primary cause of rigor mortis. Hypoxia primarily affects cellular respiration and tissue oxygenation, rather than post-mortem enzymatic processes.

C. Hypoglycemia (C) can indirectly contribute to early onset of rigor mortis. Low blood glucose levels can lead to reduced cellular energy supply, which may slow down the post-mortem enzymatic processes. However, it is less potent than hypothermia in causing early rigor onset.

D. Hypokalemia (D) can indirectly affect the rate of rigor mortis by influencing cellular ionic balance and muscle membrane excitability. However, it does not directly impact the post-mortem enzymatic processes leading to rigor mortis.

**Clinical Pearl:**
Understanding the factors affecting rigor mortis onset can help in post-mortem evaluations, particularly in forensic medicine, forensic anthropology, and forensic pathology, where it plays a crucial role in determining the time of death.