From this interesting article:https://examine.com/supplements/L-Carnitine/
If you scroll way down to Scientific Research--Table of Contents--Itneractions w/Hormones--Androgens:
9.1. Androgens
Supplemental L-Carnitine L-Tartrate at 2g daily has been shown in vivo to increase the density of Androgen Receptors in muscle cells over 21 days.[SUP][203][/SUP] Although this mechanism would not increase testosterone levels per se, it may increase the effects of testosterone as they are vicarious through its receptors.
2g L-Carnitine L-Tartrate does not further increase testosterone levels that are induced by exercise after 3 weeks supplementation in healthy males[SUP][190][/SUP] and still does not increase test in a population of men going through andropause (male equivalent of menopause) despite controlling other symptoms.[SUP][204][/SUP] In one rat study, it was noted that although Acetyl-L-carnitine did not increase testosterone that it prevented the decline of testosterone associated with chronic stress.[SUP][205][/SUP]
Supplementation may be a decent adjunct to a testosterone boosting protocol, but aside from a lack of evidence on its mechanisms, it does not seem to boost testosterone itself.
9.2. Growth Hormone
L-Carnitine L-Tartrate, at 2g daily over 3 weeks, was able to increase levels of IGF Binding Protein-3 that are induced by exercise for about 180 minutes. This theoretically may increase the effects of IGF-1 and IGF-2 by giving them more time in the blood.[SUP][190]
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14.7. DHEA
It has been noted that DHEA can increase sensitivity of red blood cells to oxidative stress at concentrations thought to be relevant to supplementation[SUP][238][/SUP] (higher concentrations of 2mM induce nonoxidative cell death, but are not thought to be practically relevant to oral supplementation of standard doses[SUP][239][/SUP]) while L-carnitine appears to exert antioxidative effects at the level of the red blood cell membrane[SUP][240][/SUP] which may result in an increase in cell survival in vitro.[SUP][241][/SUP]
One study in rats tested both L-carnitine L-tartrate (195mg/kg in the drinking water) and DHEA sulfate (1mg/kg) noted that, while neither agent alone influenced red blood cells, that the combination led to a minor reduction in both red blood cell count (12.1%) and hematocrit (9.7%) despite hemoglobin and other erythrocytic indices being unaffected in all groups.[SUP][118][/SUP]
It is possible for L-carnitine and DHEA to have interactions at the level of the red blood cell, although the clinical relevance of this information (beneficial, inert, or harmful) is not yet known and more data required
GPLC is a Glycine amino acid, bound to a carnitine molecule that is esterified to a short chain fatty acid. When Propinoyl-L-Carnitine reaches the mitochondria, it gets metabolized into L-carnitine and propionyl coenzyme A.[SUP][42][/SUP][SUP][43][/SUP] Propionyl coenzyme A is relevant as it gets converted into succinyl coenzyme A and thus succinate, which is an intermediate in the TCA cycle. Due to providing succinate as well as carnitine, supplemental GPLC can provide an anaplerotic effect.[SUP][44][/SUP]
The initial stages of metabolism are undergone by the enzyme Carnitine acetyltransferase, the same enzyme that mediates the breakdown of ALCAR to L-carnitine.[SUP][45][/SUP]
In practice, Propionyl-L-Carnitine appears to be more effective than L-Carnitine on matters related to blood flow and regulation. The most significant usage is seen with Intermittent Claudication where PLC exerts more benefit than Carnitine even on a molar basis, suggesting synergism between the Propionyl group and the Carnitine group.[SUP][46][/SUP] GPLC has also been used to increase Nitric Oxide production in sedentary men[SUP][47][/SUP] and athletes at doses of 3-4.5g daily.[SUP][48]
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