Melatonin

Melatonin is an indoleamine synthesized from serotonin in the pineal gland under the control of the suprachiasmatic nucleus (SCN), rising at dusk and peaking around 02:00–04:00. It's the body's master chronobiotic — a signal that translates "it is dark" into coordinated shifts across sleep architecture, core temperature, blood pressure, GH pulsatility, and redox state. At supplemental doses it reproduces and amplifies those signals, which is why the same molecule shows up in sleep, on-cycle BP, GH-stacking, and topical hair protocols.

MT1 / MT2 Receptor Signalling — the Sleep and Clock Machinery#

Melatonin acts through two Gi/o-coupled GPCRs expressed densely in the SCN and throughout the CNS:

• MT1 (MTNR1A): reduces neuronal firing in the SCN, lowers core temperature, and drives the acute sleep-onset effect most users feel 20–40 minutes after dosing.
• MT2 (MTNR1B): phase-shifts the circadian clock. This is the chronobiotic action — the reason a low dose taken in the early biological evening advances sleep onset, while the same dose taken after midnight phase-delays you and wrecks the next night.

Practical consequence: timing matters more than dose. A 0.3 mg dose at the right time outperforms a 10 mg dose at the wrong time. Zhdanova's work made this explicit — physiological-range dosing is sufficient to restore sleep architecture in adults with blunted endogenous profiles:

"A dose of 0.3 mg restored melatonin profiles to those observed in young adults and improved sleep efficiency by decreasing sleep onset latency." — Zhdanova IV et al., J Clin Endocrinol Metab (2001)

Somatotropic (GH) Axis Potentiation#

This is the mechanism physique-focused users care about. Melatonin attenuates hypothalamic somatostatin tone and sensitizes the pituitary to GHRH, amplifying both spontaneous and stimulus-evoked GH pulses. Taken 30–60 minutes before a bedtime GHRH+GHRP shot (or endogenous sleep-onset pulse), it stacks with — rather than competes against — the natural nocturnal GH burst.

"Oral ingestion of 5 mg melatonin 60 minutes before exercise significantly enhanced the GH response to resistance exercise in healthy men." — Meeking DR et al., Eur J Endocrinol (1999)

The practical payoff: better recovery, better sleep-phase GH exposure, and a clean synergy with CJC-1295 / ipamorelin or low-dose rhGH run pre-bed. This is also why the "GH-stack dose" (3–5 mg) is legitimately higher than the "sleep dose" (0.3–1 mg) — you're targeting a different effect.

Antioxidant and Vascular Actions#

Melatonin is a direct radical scavenger — it neutralizes hydroxyl, peroxyl, and peroxynitrite radicals without needing a recycling cofactor — and it upregulates the endogenous antioxidant enzymes SOD, catalase, and GPx. In vascular tissue this translates to reduced oxidative load on the endothelium and a measurable nocturnal BP drop, which is the mechanism anyone running harsh orals or high-dose tren should care about:

"Nightly controlled-release melatonin for 3 weeks reduced nocturnal systolic and diastolic blood pressure by 6 and 4 mmHg, respectively, as compared to placebo." — Scheer FAJL et al., Hypertension (2004)

6/4 mmHg is adjunctive, not primary — it doesn't replace telmisartan on a real cycle — but it layers cleanly with one and costs nothing.

Peripheral Tissue Effects: Scalp and Dermal Papilla#

MT1 and MT2 are expressed in the dermal papilla and outer root sheath of the hair follicle. Topical melatonin appears to extend the anagen (growth) phase and reduce oxidative stress on the follicle — a useful, low-risk adjunct in an AGA stack rather than a standalone therapy:

"Topical melatonin increased anagen hair rate, reduced telogen hair, and was associated with a reduction in hair loss in patients with androgenetic alopecia." — Fischer TW et al., Int J Trichology (2012)

Effect size is modest. Think of 0.1% scalp melatonin as an add-on layered onto minoxidil + finasteride (or topical fin/dut + an AR antagonist like RU58841 if you're running AAS), not as a replacement for any of them.

Pharmacokinetic Reality Check#

Oral melatonin hits a pharmacokinetic wall that dictates how you dose it:

"The average absolute bioavailability of oral melatonin was 15%, with a marked range from 9 to 33% due to extensive first-pass metabolism." — DeMuro RL et al., J Clin Pharmacol (2000)

Two consequences follow directly:

First-pass metabolism runs primarily through CYP1A2, which is why smokers see blunted plasma levels and why fluvoxamine (a CYP1A2 inhibitor) can raise melatonin AUC by more than an order of magnitude — a genuine interaction to avoid. Standard IR oral is a sleep-onset tool, not a sleep-maintenance tool; if you wake at 03:00, a 22:00 IR dose is long gone and you need extended-release or a different strategy.

Common (most users)#

• Morning grogginess / "melatonin hangover" — almost always a dose problem, not a melatonin problem. Drop from 5–10 mg to 0.5–1 mg and it resolves within a night or two. Sublingual or liquid drops help if you're dialing in micro-doses.
• Vivid dreams — dose-dependent and harmless. Some users enjoy this; if you don't, drop the dose.
• Transient headache or lightheadedness — usually at first dose or after a dose increase. Hydrate and reassess at the lower end of the ladder.
• Mild next-morning "flat" mood at chronic high doses — back off to 0.3–1 mg. Physiologic dosing does not produce this.
• Mild hypotension / cool feeling on lying down — mechanism is real (nocturnal BP drop of ~6/4 mmHg in hypertensives):

"Nightly controlled-release melatonin for 3 weeks reduced nocturnal systolic and diastolic blood pressure by 6 and 4 mmHg, respectively, as compared to placebo." — Scheer FAJL et al., Hypertension (2004)

Welcome on cycle, worth noting if you're already on tadalafil daily, telmisartan, or clonidine. Stand up slowly if stacked.

Uncommon (dose-dependent or individual)#

• Phase-delay / worsened insomnia from late dosing — taken after 01:00 it shifts your clock the wrong way. Dose 30–60 min before target bedtime, not when you're already late.
• Daytime sedation from extended-release at too high a dose — drop the CR dose or switch to IR.
• Mild prolactin bump — irrelevant at 0.5–5 mg; worth noting if you're already fighting prolactin on 19-nors and running caber/P5P.
• Blunted LH pulse frequency at chronic supraphysiologic doses — documented in animal models, not a known problem at 0.5–5 mg nightly in humans, but a reason to be skeptical of the 20–60 mg "megadose for longevity" crowd if you're natty or on a SERM protocol trying to preserve HPG function.
• Label inaccuracy from low-quality suppliers — US gummies have been assayed at 50–400% of stated content. Not a pharmacology issue, a QC issue. Use USP-verified tablets or liquid, skip gummies.
• GI upset — rare, take with a small amount of food if it happens.

Rare but serious#

• Autoimmune flare — theoretical immune-stimulatory concern in lupus, RA, Crohn's, Hashimoto's. Rare in practice but plausible enough that anyone with active autoimmune disease should skip it or clear it first.
• Altered INR on warfarin — isolated case reports. If you're on warfarin, monitor INR when starting or stopping.
• Paradoxical agitation / depressed mood — uncommon, more often reported in kids than adults. If mood clearly worsens across the first 2 weeks, stop.
• Seizure-threshold lowering — weak signal in epilepsy literature, mostly at high doses. Relevant only if you have a seizure disorder.

Hard contraindications#

• Fluvoxamine — CYP1A2 inhibition raises melatonin AUC up to ~17×. Do not combine.
• Warfarin — only with active INR monitoring.
• Pregnancy and lactation — insufficient human safety data; skip it.
• Active autoimmune flare — do not add an immune modulator to an already-dysregulated immune system.
• Operating vehicles/heavy equipment within ~5 hours of dosing — obvious, but the 10 mg gummy crowd routinely ignores this.

Gender-specific and cycle considerations#

Dosing is the same for men and women. Women trying to conceive should know melatonin is under study as an ovulation modulator — neither clearly helpful nor harmful at 0.3–3 mg, but it's not a neutral molecule at the ovary and isn't something to take "just in case" during a conception window.

No PCT considerations. Melatonin does not suppress the HPTA at physiologic-to-moderate doses and can be run continuously or cycled as desired. On-cycle use as a BP and oxidative-stress adjunct is one of its better physique-focused applications, and it stacks cleanly with pre-bed GH/GHRP protocols without interfering with recovery bloodwork.