L-carnitine supplementation for the management of fatigue in patients with hypothyroidism on levothyroxine treatment [Letter to the Editor]

Abstract

mately 10% of hypothyroid patients, especially those with no remnant thyroid tissue (i.e., post-radioiodine, post-thyroidectomy hypothyroidism) [3]. This residual symptomatology consists essentially in physical and/or mental fatigue, and can be addressed by adding L-T3 to L-T4 [3].Within the limits of words and references permitted by the journal and not to give complete details that would preclude publication of a full paper, we would like to give some information in support of the An and colleagues' article [1]. We have a number of hypothyroid patients who have taken 2 g/d L-carnitine even for longer than 12 weeks, and we confirm the benefit in terms of physical and mental fatigue. The benefit is observed particularly in premenopausal women with postoperative hypothyroidism. Thus, it is not surprising for us that women and postoperative hypothyroidism accounted for 100% and approximately two-thirds of the subgroup that improved, but approximately 75% and 40% of the subgroup who did not (table 3 of ref. 1).A mechanistic explanation for the efficacy of L-carnitine we wish to offer has to do with previous research on the modulation of L-carnitine on glucocorticoid action [4]. L-carnitine promotes nuclear translocation of glucocorticoid receptor-α (GRα), an important activating step of the glucocorticoid signalling. After nuclear translocation, homodimers of the activated GRα modulate the transcription of many responsive genes by binding to specific DNA-associated glucocorticoid-responsive elements (GREs) in the promoters of these genes. Similarly to glucocorticoids, L-carnitine suppressed the release of tested cytokines (tumor necrosis factor-α [TNFα] and interleukin-12 release by the tested cells (human primary monocytes) [4]. The glucocorticoid-mimetic activity of L-carnitine, resulting from stimulated transcriptional activity of GRα, would have not been predicted by the inhibiting effect of L-carnitine on glucorticoid entry into cells [4]. Now, considering that (i) cytokines are pathogenetically involved in fatigue and other neuropsychological disorders, (ii) GRα-mediated action of glucococorticoids results in "energizing" effects [5], and (iii) glucocorticoids extert a well-known inhibition of TSH secretion, it cannot be coincidental that the improved subgroup had an almost 3-fold lower concentration of TSH compared to the non-improved subgroup [1]. Dear Editor,We have read with interest the nice article by An et al. [1], and thank them for having cited some papers of our team, but not one [2]. That paper [2] not only mentions the wide range of patients who may benefit of L-carnitine supplementation, but also underscores that on some thyroid hormone targets L-carnitine acts as an antagonist, while on others as an agonist. We would like to discuss some aspects that were missed there [1].We start with somewhat minor comments. First, we continue to confirm that L-carnitine has minimal, if any, side-effects. Second, the formulation of L-carnitine we use (one ampoule of 1 mg given twice a day) is more practical t...

Nutraceutical Supplements in the Thyroid Setting: Health Benefits beyond Basic Nutrition

“…In subgroups, both the physical and mental fatigue scores improved significantly in patients younger than 50 years and those with free T3 ≥ 4.0 pg/mL by treatment with l -carnitine compared with placebo. Other case-based studies have indicated a benefit from l -carnitine on hypothyroid symptoms, but all of them have been case-based [45], while other studies may support benefits in the corticosteroid hormone setting [46].…”

Impact of Maternal Lifestyle and Dietary Habits during Pregnancy on Newborn Metabolic Profile

“…Carnitine determines good cardiac function and a reduction in oxidative stress, inflammation, and necrosis processes. The relationship between carnitine and thyroid function comes from clinical studies showing the antagonistic thyroid hormone action effects of C0 [ 19 , 20 , 21 , 22 ] and a positive correlation between urinary carnitine with serum thyroxin concentration [ 23 ]. In our study, C0 was lower in newborns whose mothers used iodized salt during pregnancy ( Figure 2 C).…”

Fish and the Thyroid: A Janus Bifrons Relationship Caused by Pollutants and the Omega-3 Polyunsaturated Fatty Acids

“…Such favorable effects of the omega-3 PUFA on consequences in the peripheral tissues that are caused by opposite states of thyroid dysfunction confer to the omega-3 PUFA a modulatory role that is reminiscent of another dietary nutrient, L-carnitine. Indeed, beneficial effects of L-carnitine were reported both in the hyperthyroidism setting ( 144 , 145 ) and in the hypothyroidism setting ( 146 , 147 ), with a modulatory role also demonstrated in the tissue glucocorticoid hormone action ( 148 ).…”