Licorice (Glycyrrhiza glabra 2)

Indications

Elevated testosterone and prolactin, metabolic syndrome, polycystic ovary syndrome (PCOS).

Mechanism of Action

Researchers report that Glycyrrhiza helps normalize elevated testosterone by several mechanisms including reducing the synthesis of testosterone¹ and blocking the dehydrogenase enzymes^2,3 that help synthesize it^4,5; blocking 5α-reductase enzymes that convert testosterone to the more active dihydrotestosterone⁶; enhancing the metabolism of testosterone; and reducing cellular response to testosterone at testosterone receptors.⁷

Evidence-Based Research

A saponin, a steroid-like molecule in Glycyrrhiza named glycyrrhizic acid, is credited with an ability to improve insulin resistance⁸ and fat metabolism in animal models of metabolic syndrome.⁹ Glycyrrhiza reduces inflammation and supports function in animal models of diabetic kidney damage,¹⁰ improves insulin sensitivity, reduces fat deposition in tissues,⁹ and suppresses the accumulation in abdominal fat.¹¹

Animal studies suggest that Glycyrrhiza can reduce elevated androgens,⁷ and one human study showed Glycyrrhiza to decrease serum testosterone in women as well.¹ Glycyrrhiza is a traditional Japanese herbal medicine for infertility and researchers have shown it to promote ovulation and menstruation in amenorrhoeic women¹² as well as women with PCOS.¹³ Glycyrrhiza is often used in Japan combined with peony to treat PCOS in a traditional herbal medicine called Shakuyaku-Kanzo-To, which is reported to reduce elevated testosterone.¹⁴ One early study reported Shakuyaku-Kanzo-To to be more effective in women with generalized diffuse cysts than with peripheral cysts, a finding that has not been further investigated.¹³

Glycyrrhiza may also reduce elevated prolactin. An undesirable side effect of some drugs, particularly antipsychotics, is prolactin elevation and the resulting cessation of menses. The combination of peony and Glycyrrhiza has been shown to reduce elevated prolactin in women with hyperprolactinemia induced by the antipsychotic medication risperidone.¹⁵

One clinical study evaluated the effects of Glycyrrhiza in women with PCOS taking spironolactone, a synthetic drug capable of blocking androgen receptors and thereby reducing elevated testosterone and other androgens, but also impairing the regulation of body minerals via mineralocorticoid receptor agonism. Glycyrrhiza was found to reduce such side effects and support regular menses.¹⁶ Glycyrrhiza may be an effective alternative to spironolactone therapy, as licorice itself may reduce elevated testosterone.

Safety in Pregnancy and Breastfeeding

Glycyrrhiza is not considered to have the risk of inducing miscarriage or acting as an abortifacient, but it has been associated with an increased risk of preterm delivery. In general, Glycyrrhiza is demonstrated to have a spasmolytic action on the uterus.¹⁷ Tissue studies suggest licorice to possibly inhibit oxytocin, prostaglandin, and KCl-induced uterine contractions¹⁸ as well as those induced by calcium channel activation, nitric-oxide synthase, or cyclooxygenase.¹⁹ However, several outcome studies have reported a higher incidence of threatened miscarriages and preterm labors among regular users of Glycyrrhiza compared with those women not exposed to these herbs during pregnancy, although the sample size was small and the confounding factors numerous and complex.²⁰ “Heavy” Glycyrrhiza exposure (>500 mg of glycyrrhizin per week) was associated with a greater risk of preterm delivery in one outcome study,²¹ without evidence of effects on birth weight or maternal blood pressure.²² Another outcome study reviewed data on 185 pregnant women who used Glycyrrhiza-containing cough and cold formulas with a maximum dose of 2104 mg/day, anywhere between the 4th day and 25th week of gestation. The rate of stillbirths was marginally higher among women who took Glycyrrhiza compared with those who did not, and there was no evidence of teratogenic effects.²³

Synthetic glucocorticoids administered during pregnancy to improve fetal lung maturity in threatened preterm birth have been shown to reduce birth weight and head circumference, but they have not been linked to gross changes in long-term health to date. 11β-Hydroxysteroid dehydrogenase type 2 enzymes (11β-HSD2), discussed above, are also active in the placenta and may become up-regulated during pregnancy if a woman is exposed to stress, as these enzymes promote glucocorticoid production.

Animal studies show that long-term stress alters the hypothalamic–pituitary–adrenal axis and that Glycyrrhiza-like synthetic glucocorticoids can increase the occurrence of behavioral problems as a result.²⁴ Glycyrrhizin, a natural constituent of Glycyrrhiza, potently inhibits 11β-HSD2, thereby reducing the fetoplacental barrier to the higher maternal cortisol levels. Maternal consumption of glycyrrhizin was shown to correlate to increased salivary cortisol levels in newborns, compared with newborns whose mother had zero exposure during pregnancy.²⁵ Another human outcome study reported that prenatal exposure to Glycyrrhiza exerted detrimental effects on cognitive performance, as determined by standardized neuropsychological assessment tests and the report of psychiatric symptoms. Those with zero to low exposure (0–249 mg/week) scored better than those with high exposure (≥500 mg/week).²⁶

One rat study reported Glycyrrhiza gavage at a dose of 100 mg/kg for 7 days to significantly increase the teratogenicity of cyclophosphamide by inducing cytochrome p450 enzyme conversion of the compound into toxic metabolites.²⁷ Other human outcome studies however have not observed licorice to have teratogenic activity.

Thus, it may be concluded that Glycyrrhiza should be avoided in pregnancy in anything greater than an occasional cup of tea. High doses, concentrated products, and daily consumption of Glycyrrhiza should be avoided during pregnancy.

General Safety

There have been widely publicized reports that Glycyrrhiza may lead to an increase in blood pressure, although the actual occurrence of this side effect is quite rare. Nonetheless, high blood pressure is a concern for some women with metabolic syndrome. Studies are now indicating that Glycyrrhiza may aggravate high blood pressure more often in those with a preexisting complex adrenal disorder involving altered potassium levels^{28,29,30,31,32} or in those with a particular isoform of the 11β-DHS enzymes. Defects in the 11β-HSD2 enzyme contribute to hypertension and may make some people more sensitive to the hypertensive effects of salt and Glycyrrhiza because the kidneys express high levels 11β-HSD2 and are the principal source of cortisone in humans.³³

Interestingly, Glycyrrhiza has in fact been reported to reduce blood pressure in animal models with metabolic syndrome.³⁴ However, the side effect of elevated blood pressure remains unpredictable, so people using Glycyrrhiza supplements regularly should monitor their blood pressure. People with abnormally low potassium levels should avoid Glycyrrhiza because of the possibility of serious muscle weakness and high blood pressure. Do not consume more than 2 or 3 cups of Glycyrrhiza tea per day unless under a physician’s guidance. One clinical study investigating the benefits of Glycyrrhiza on mineralocorticoids in women taking spironolactone reported no subjects to experience hypertension as a side effect.¹⁶ There has been one anecdotal case report of acute urinary retention associated with severe hypokalemia possibly associated with licorice use in a pregnant woman.³⁵ Various genotoxic studies have indicated that glycyrrhizin is neither teratogenic nor mutagenic and may possess antigenotoxic properties under certain conditions.³⁶

Glycyrrhizin/glycyrrhizic acid may induce edema, hypertension, and hypokalemia in patients treated with higher doses and long-term administration, all as a side effect of pseudoaldosteronism caused by the 11β-HSD inhibition. There are cases of Glycyrrhiza aggravating pseudohyperaldosteronism.³⁷ Hypokalemic periodic paralysis, a rare disorder consisting of sudden episodes of muscle weakness with areflexia involving all four limbs that spontaneously resolves in several hours to several days, may be associated with heavy Glycyrrhiza ingestion in some people.³⁸

Dosage

Traditional medicines include teas, syrups, and powders at a wide variety of dosages, depending on whether it is being used as a lead or supportive herb within the formula.

Modern encapsulations will use 250–1000 mg in a single dose that is repeated several times a day. As this herb has potential for toxicity symptoms, use caution if exceeding doses greater than 4 g/day continuously.

Based on the in vivo and clinical evidence, an acceptable daily intake of isolated glycyrrhizin, one that will not typically cause sodium retention or hypertension, is 0.015–0.229 mg /kg body weight/day.³⁶

Traditional Uses

Glycyrrhiza is a rhizome that has been used since ancient times in traditional Chinese medicine and in ancient Egyptian, Greek, and Roman healing traditions for numerous medicinal uses. In China, it has been referred to as “the great harmonizer” because of the belief that it can go everywhere in the body and pull together the actions of other herbs in botanical formulas. Licorice seems to deserve this reputation because it can be used for ulcers, allergy, viral infections, fatigue, hepatoprotection, adrenal disorders, infertility, and numerous hormonal problems. Several licorice-based medicines have been introduced including a Japanese glycyrrhizin preparation used clinically as an antiallergic and antihepatitis agent and a remedy for gastric ulcer marketed in the Netherlands in 1940s. Licorice also has a long-standing reputation as an emergency remedy in China for acute pituitary failure such as postpartum Sheehan’s syndrome.³⁹

References