Final answer:
The hormone most closely related to sleep patterns is melatonin, which is secreted by the pineal gland and helps regulate the circadian rhythm. Its production is affected by light exposure, with increased production in darkness and inhibited production in light.
Step-by-step explanation:
The hormone most closely related to one's sleep patterns is melatonin (D). Melatonin is synthesized from the amino acid tryptophan and is secreted by the pineal gland. It plays a crucial role in regulating the circadian rhythm or the sleep-wake cycle. This process is influenced by the level of light, with darkness stimulating melatonin production and light inhibiting it. Serotonin, which is a precursor for melatonin, can affect this production. Other hormones like epinephrine, norepinephrine, and dopamine, which are derived from tyrosine, have different functions primarily related to metabolism, the fight-or-flight response, and neurotransmission, respectively.
In contrast, as light levels decline, such as during the evening, melatonin production increases, leading to higher blood levels of melatonin and causing drowsiness. Furthermore, during winter, less sunlight can alter the daily cycle of melatonin production, leading to trouble sleeping for some individuals. Melatonin supplements are sometimes used to aid with sleep problems.