T Nation

Melatonin and Shrunken Nuts

Effects on Reproduction and Sexual Function

Administration of melatonin inhibits ovulation in humans by reducing luteinizing hormone concentrations. Thus, the melatonin can be viewed theoretically as a potential contraceptive.26 Despite claims, no data support melatonin’s use in prolonging sexual vitality in humans. In animal studies, gonadal shrinkage has been associated with melatonin administration.1,17


Melatonin has really helped me get the sleep I need, especially on nights after brutal workouts. Unfortunately it lowers LH and therefore testosterone. I didn’t realize this unitl my wife and I tried to conceive. My sperm count was very low. 6 months after stopping melatonin, my count is normal. After doing further research I found it acts like estrogen in women. Which explains why my wife gained weight on it. It was actually acting like a birth control pill. Thereby hindering our efforts to make a little T-Man. Just and FYI for fellow T-Men and T-Vixens. It pays to do your research before you begin popping pills.

Wow! I likewise having sleeping troubles and was looking into getting some melatonin. So much for that one.

Appreciate it.

Well I’ll be damned!! This really pisses me off! I’ve been using melatonin for the past 9 months or so (4-5) times per week. I thought that I had found a miracle supp. I mean, I liked this stuff ALOT! Great find on this research though, this is why I cruise the forums. But thanks for ruining my night.

I’ve read about melatonin being an effective contraceptive as well.

Not getting enough sunlight in the winter may raise melatonin levels. I’ve read it may lower testosterone levels due to this. It’s the theorized mechanism behind Seasonal Affective Disorder. High melatonin levels may result in depression.

The spring fever people experience after winter due to increased sunlight may be caused by lowered melatonin, which in turn may raise testosterone.

I’ve read that light therapy may increase LH secretion. The study didn’t imply or measure the effects on testosterone though.

I’m a little fuzzy on the relation between melatonin and testosterone though. I’d have to check some references to be more sure.

i sometimes take 3mg with my ZMA dosage before bedtime. that might explain my lack of morning erection. i will monitor this more carefully if this is always the case. Anywyas, i believe that sleep is very important and you can always take some other supps to counteract the affect of the melatonin like tribex, avena sativa and long jack. laters pk

Here’s a good question for some of the staffers at T-Nation… Since Biotest M binds at the estrogen receptor sites, would taking M before taking melatonin help to mitigate reduction in LH?

[quote]bckdarkjedi wrote:
Here’s a good question for some of the staffers at T-Nation… Since Biotest M binds at the estrogen receptor sites, would taking M before taking melatonin help to mitigate reduction in LH?[/quote]

Well, I went over melatonin briefly in a past column. However, I’ll say again that provided that you’re using a small amount (1-5 mg) and aren’t using it chronically, I wouldn’t worry about it.

Here are a few references including one that I had used in my column. You’ll see that although some data conflicts, the majority of it indicates it’s not a concern, especially if, as I said, you’re only using the usual amount and aren’t using it every day of your life.

In any event, although I haven’t looked in to it in depth, just from skimming over things, it would appear that it could potentially decrease LH via the increase in prolactin levels. It could also accomplish such effects by interfering with cAMP accumulation. There could be a few mechanisms actually.

In any event, M could potentially help via two mechanisms, i.e., decreasing prolactin as well as containing an estrogen antagonist. However, in any case, I think the better approach is simply using the normal dose of melatonin, only when you really need it.

J Mol Neurosci. 1999 Feb;12(1):75-80.

Melatonin administered in the afternoon decreases next-day luteinizing hormone levels in men: lack of antagonism by flumazenil.

Luboshitzky R, Shen-Orr Z, Shochat T, Herer P, Lavie P.

Endocrine Institute, Haemek Medical Center, Afula, Israel.

The role of melatonin in the regulation of human reproduction remains unclear. In the present study, we examined the influence of exogenous melatonin on pulsatile luteinizing hormone (LH), diurnal rhythm of testosterone, and endogenous melatonin profile in six healthy young adult males. To test the hypothesis that the effect of melatonin on LH or testosterone secretory patterns may be mediated through the benzodiazepine-(BNZ) gamma-amino-butyric acid (GABA) receptor complex, a benzodiazepine receptor antagonist (Flumazenil) was administered. The study design comprised four 10-h (4:00 PM-2:00 AM) testing periods. During each experimental period, subjects were given an oral dose of placebo, or 3 mg melatonin or 10 mg flumazenil, at 5:00 PM, in a randomized, double-blind, partially repeated Latin square design in the following combinations: placebo-placebo, placebo-melatonin, flumazenil-placebo, and flumazenil-melatonin. The following day, serum samples were obtained every 20 min between 4:00 PM and 2:00 AM in a controlled light-dark environment for the determination of LH and melatonin levels. Serum testosterone concentrations were determined every 20 min between 7:00 and 8:00 AM and 7:00 and 8:00 PM. A significant decrease in mean serum LH levels (p < 0.02) was observed in the melatonin-treated groups as compared with placebo-flumazenil groups. There was no change in LH pulse frequency, testosterone levels, or in melatonin onset time and amplitude. No additional effect of flumazenil on LH or testosterone levels was observed. These data indicate that an evening melatonin administration decreases the next-day LH secretion in normal adult males without altering testosterone levels or the endogenous nocturnal melatonin secretory pattern. This effect of melatonin is not mediated through the benzodiazepine-GABA receptor complex.

Hum Reprod. 2000 Jan;15(1):60-5.

Long-term melatonin administration does not alter pituitary-gonadal hormone secretion in normal men.

Luboshitzky R, Levi M, Shen-Orr Z, Blumenfeld Z, Herer P, Lavie P.

Endocrine Institute, Haemek Medical Center, Afula 18101, Israel.

The role of melatonin in the regulation of reproduction in humans is still controversial. In the present study the effects of melatonin were examined, 6 mg given orally every day at 1700 h for 1 month in a double-blind, placebo controlled fashion, on the nocturnal secretory profiles of luteinizing hormone (LH), follicle stimulating hormone (FSH), testosterone and inhibin beta in six healthy adult men. Serum concentrations of LH, FSH, testosterone and inhibin beta were determined before and after treatment every 15 min from 1900 to 0700 h over 3 nights in a controlled dark-light environment with simultaneous polysomnographic sleep recordings. The following sleep parameters were determined: total recording time, sleep latency, actual sleep time, sleep efficiency, rapid eye movement (REM) sleep latency and percentages of sleep stages 2, 3/4 and REM. There were no statistically significant differences in all sleep parameters between baseline and placebo or between baseline and melatonin except for longer REM latency and lower percentage REM at baseline than under melatonin treatment. These are explained as reflecting first-night effect at baseline. The mean nocturnal LH, FSH, testosterone and inhibin beta integrated nocturnal secretion values did not change during the treatment period. Likewise, their pulsatile characteristics during melatonin treatment were not different from baseline values. Taken together, these data suggest that long-term melatonin administration does not alter the secretory patterns of reproductive hormones in normal men.

Hum Reprod. 1993 Nov;8(11):1819-22.

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)
Clin Endocrinol (Oxf). 1986 Apr;24(4):375-82.

The effects of exogenous melatonin on endocrine function in man.

Wright J, Aldhous M, Franey C, English J, Arendt J.

At two different times of year (spring and autumn) an oral preparation of the pineal neurohormone melatonin, or placebo, was administered to 12 healthy volunteers (10 men and two women in spring: the same group minus one man in autumn) daily at 1700 h for 1 month (spring), or 3 weeks (autumn) using a double-blind cross-over protocol. The daily dose was 2 mg melatonin in 5 ml corn-oil, and placebo consisted of the vehicle only. In spring the anterior pituitary hormones LH, PRL, GH together with T4, cortisol, testosterone and melatonin were measured at 1- to 6-h intervals for 24 h in plasma on the day following the last dose. In autumn PRL, cortisol and melatonin levels were measured on the last day of treatment. Subjective fatigue, mood and sleep records were kept throughout the studies. Melatonin increased early evening fatigue and actual sleep, but had no effect on mood: these results are reported in full elsewhere. Melatonin administration had no effect on the levels or 24-h rhythm of LH, GH, T4, testosterone or cortisol. An earlier fall in the nocturnal PRL was observed on both occasions. Overall PRL levels were higher in spring than in autumn. In five of the subjects, the secretion of endogenous melatonin was advanced by 1-3 h in the presence of exogenous melatonin. These observations suggest that the potential therapeutic use of melatonin as a hypnotic or in the treatment of jet lag is unlikely to be complicated by undesirable endocrine effects.

: Neuroendocrinology. 1987 Aug;46(2):125-30.

A pharmacological dose of melatonin increases PRL levels in males without altering those of GH, LH, FSH, TSH, testosterone or cortisol.

Waldhauser F, Lieberman HR, Lynch HJ, Waldhauser M, Herkner K, Frisch H, Vierhapper H, Waldhausl W, Schemper M, Wurtman RJ, et al.

Since reports on the influence of melatonin (aMT) on the human endocrine system are scant and inconsistent, the effect of an acute, pharmacological dose of aMT on various hormone levels in healthy males was examined in 3 different experiments. Experiment I: 80 or 240 mg of crystalline aMT were administered per os to 8 volunteers. Before, during and after this treatment, serum levels of aMT, PRL, LH, FSH and testosterone were examined. Although aMT increased at least 1,500-fold over basal levels, only PRL was significantly and consistently elevated after aMT treatment, whereas serum levels of the other hormones were not altered. Experiment II: in 2 subjects, the pulsatile secretion pattern of LH was monitored for 6 h before and 6 h after aMT administration (240 mg p.o.). Neither the amplitude nor the frequency of LH pulses was influenced by the pineal hormone. Experiment III: in 14 volunteers, serum PRL, GH, TSH and cortisol concentrations were examined, once after oral administration of 240 mg aMT and once after placebo. Serum PRL levels were significantly higher after aMT than after placebo; GH showed a slight but not significant trend towards elevation after aMT, whereas other hormones were not altered. An acute pharmacological dose of aMT causes isolated elevation of serum PRL levels and may slightly increase GH. Hormones of the pituitary gonadal axis as well as TSH and cortisol are not altered by aMT.

1: J Clin Endocrinol Metab. 1977 Oct;45(4):768-74.

The effects of oral melatonin on skin color and on the release of pituitary hormones.

Nordlund JJ, Lerner AB.

We studied the effects of prolonged ingestion of melatonin, 1 g per day, on skin color and the serum levels of pituitary hormones in 5 human subjects with hyperpigmented skin. Melatonin lightened hyperpigmented skin of one patient with untreated adrenogenital syndrome, but had no effect on three patients’ skin with idiopathic hyperpigmentation and one patient with treated Addison’s disease. Melatonin appeared to depress the level of luteinizing hormone (LH) in serum and may have inhibited in some patients the release of growth hormone from the pituitary gland after stimulation by stress or L-dopa. The subjects all noted increased drowsiness but through studies on the eyes, liver, kidneys, and bone marrow revealed no other evidence of toxicity.

PMID: 914981 [PubMed - indexed for MEDLINE]