1 reply to this topic

[NickCage]

I wondered if anyone could shed some light on this, does melatonin lower testosterone. I was watching a video on youtube and it mentioned it did

http://www.youtube.c...re=channel_page at 1.20min

[VespeneGas]

I wondered if anyone could shed some light on this, does melatonin lower testosterone. I was watching a video on youtube and it mentioned it did

http://www.youtube.c...re=channel_page at 1.20min

He says that rozerem/ramelteon is pharmaceutical melatonin, which is incorrect. It is a MT1 and MT2 receptor agonist, e.g. a synthetic drug that works through melatonin receptor activation.

He then says that melatonin works only intermittently, unlike zolpidem (ambien) which is, if not a joke, laughably false. I've gotten good results from taking 300 mcg of melatonin each night for 2 years. Zolpidem builds tolerance so fast that I was taking 2 pills to get half the quality sleep within one week of beginning the drug. Melatonin receptors are not subject to downregulation AFAIK, whereas GABA(a) receptors are exquisitely so capable.

As to your original question, it appears that people with low testosterone (in this case due to GnRH deficiency), melatonin levels are elevated, which is corrected by HRT.

The title of the following aspect indicates that melatonin potentiates the ability of exogenous testosterone to inhibit LH release, which might indicate that supplemental melatonin interferes with LH, but may not. From the meat of the abstract, it would appear that retardedly high doses of melatonin (100 mg per day) did NOT impact T or LH levels.

Melatonin potentiates testosterone-induced suppression of luteinizing hormone secretion in normal men.
Anderson RA, Lincoln GA, Wu FC. MRC Reproductive Biology Unit, Centre for Reproductive Biology, Edinburgh, UK.

A total of 12 healthy adult men were recruited to investigate the effect of exogenous melatonin on the sensitivity of the hypothalamo-pituitary axis to sex steroid negative feedback. The experiment consisted of a double-blind, randomized cross-over trial during which all subjects received 100 mg oral melatonin or placebo at 1600 h for 14 days. Midway through each of the two treatments (day 8), 100 mg testosterone propionate i.m. (TP) was given at 0900 h. Blood samples for the measurement of luteinizing hormone (LH), follicle stimulating hormone (FSH), prolactin, testosterone and melatonin were taken at 0900 h on days 1, 3, 5, and daily from days 8-14. An additional blood sample was taken 8 h after the administration of testosterone. The interval between the melatonin and placebo treatment periods was 2 months. The oral administration of melatonin caused a pharmacological increase in the blood plasma concentration of melatonin which was maximum at 2 h and still above normal at 24 h. The daily treatment thus resulted in persistently high circulating levels of melatonin for 14 days. This treatment had no significant effect on the secretion of LH, FSH, prolactin or testosterone based on the first week of each study (melatonin compared with placebo). The injection of TP caused a rapid 3 to 4-fold increase in the plasma concentrations of testosterone which was at a maximum at 8 h and had returned to baseline within 4 days, with a similar pattern in both the melatonin and placebo periods.(ABSTRACT TRUNCATED AT 250 WORDS)

PMID: 8288743 [PubMed - indexed for MEDLINE

This one is in dogs, and I'm not sure how closely our endocrine metabolism parallels theirs. Male dogs saw only reduction in progesterone and estrogen in this trial. Looks like they were taking about 20 mg/day, assuming 44 lb dogs.

Effect of oral melatonin administration on sex hormone, prolactin, and thyroid hormone concentrations in adult dogs - Abstracts: recently published abstracts - Brief Article

Alternative Medicine Review, Sept, 2001 by PF Ashley, LA Frank, LP Schmeitzel
OBJECTIVE: To determine the effect of oral melatonin (MT) administration on serum concentrations of sex hormones, prolactin, and thyroxine in dogs. DESIGN: Prospective study. ANIMALS: 8 male and 8 female adult sexually intact dogs. PROCEDURE: 5 male and 5 female dogs were treated with MT (1.0 to 1.3 mg/kg [0.45 to 0.59 mg/lb] of body weight), PO, every 12 hours for 28 days; the other 6 dogs were used as controls. Blood samples were collected on days 0, 14, and 28, and serum concentrations of estradiol-17 beta, progesterone, testosterone, androstenedione, 17-hydroxyprogesterone (17-HP), dihydroepiandrostenedione sulfate (DHEAS), prolactin, and thyroxine were determined. On day 5, serum MT concentrations were measured before and periodically for up to 8 hours after MT administration in 4 treated dogs. RESULTS: Female dogs treated with MT had significant decreases in serum estradiol, testosterone, and DHEAS concentrations between days 0 and 28. Male dogs treated with MT had significant decreases in serum estradiol and 17-HP concentrations between days 0 and 28. Serum MT concentrations increased significantly after MT administration and remained high for at least 8 hours. Prolactin and thyroxine concentrations were unaffected by treatment. CONCLUSIONS AND CLINICAL RELEVANCE: Melatonin is well absorbed following oral administration and may alter serum sex hormone concentrations.

It is not at all clear that melatonin supplementation, especially at rational levels, decreases total testosterone. This next one does indicate that melatonin acutely raises prolactin, which is a testosterone antagonist for several if not all intents and purposes (not sure). Assuming you get exposed to bright light upon waking, I wouldn't think this would have any serious effects other than helping to induce sleep (prolactin also being a dopamine antagonist). But I'm not an endocrinologist.

Positive relationship between the nocturnal concentrations of melatonin and prolactin, and a stimulation of prolactin after melatonin administration in young men.
Webley GE, Böhle A, Leidenberger FA. Institute for Hormone and Fertility Research, Hamburg, Federal Republic of Germany.

The relationship between the concentrations of melatonin and prolactin over the 24-h cycle has been investigated in a group of young men at three times in the year. Melatonin and prolactin showed a significant positive correlation (P less than 0.001) for all times during the 24-h period but with a greater contribution from concentrations during the nocturnal period, when both hormones were elevated. The positive correlation for nocturnal concentrations was evident in February and March (P less than 0.01) but was of greatest significance in June (P less than 0.001). In blood samples taken at 15-min intervals during the morning (0800-1200) and evening (2000-2400), melatonin and prolactin concentrations were not significantly correlated. Melatonin concentrations increased before prolactin during the evening and decreased before prolactin in the morning. Oral administration of 6 mg melatonin significantly stimulated prolactin release above concentrations measured after placebo administration, in both the morning (P less than 0.05) and evening (P less than 0.01) time periods; the prolactin response being greater in the evening. These results provide evidence for melatonin controlling the nocturnal increase of prolactin via its ability to stimulate prolactin release.

PMID: 3367257 [PubMed - indexed for MEDLINE

I wouldn't waste my time watching this (deranged?) guy's youtube videos, IMHO.