Interdependency of lithium ratio, plasma lithium level and clinical state in patients with affective disorders

Predicting response to lithium in mood disorders: role of genetic polymorphisms

Lithium is considered to be the first choice mood stabilizer in recurrent mood disorders. Its widespread and large-scale use is the result of its proven efficacy. In spite of this fact, patients have been observed to show a variable response to lithium treatment: in some cases it is completely effective in preventing manic or depressive relapses, while in other cases it appears to show no influence on the disease course. The possible definition of a genetic liability profile for adverse effects and efficacy will be of great help, as lithium therapy needs at least 6 months to be effective in stabilizing mood disorders. During the last few years, a number of groups have reported possible liability genes. Lithium long-term prophylactic efficacy has been associated with serotonin transporter protein, tryptophan hydroxylase and inositol polyphosphate 1-phosphatase variants. A number of other candidate genes and anonymous markers did not yield positive associations. Therefore, even if some positive results have been reported, no unequivocal susceptibility gene for lithium efficacy has been identified. Although the available data may not currently allow a meaningful prediction of lithium response, future research is aimed at the development of individualized treament of mood disorders, including the possibility of 'pharmacological genetic counseling'.

Risk factors of thyroid abnormalities in bipolar patients receiving lithium: a case control study

BACKGROUND

Lithium-induced thyroid abnormalities have been documented in many studies. They may occur despite normal plasma lithium levels. The objectives of this study were: 1) to determine possible relationship between lithium ratio, defined as erythrocyte lithium concentrations divided by plasma lithium concentrations, and thyroid abnormalities in bipolar patients receiving lithium and 2) to find other possible risk factors for developing thyroid abnormalities in the subjects.

METHODS

Sixty-eight bipolar patients receiving lithium therapy were enrolled in a cross-sectional evaluation of thyroid function test and thyroid size. Patients were divided into two groups based on their thyroid function tests and thyroid sizes. Erythrocyte and plasma lithium concentrations were determined by atomic absorption spectrometry for each patient. Lithium ratio was then calculated.

RESULTS

No significant differences were found between age, positive family history of affective disorder, plasma lithium concentration, erythrocyte lithium concentration, and lithium ratio comparing the two groups. Thyroid abnormalities was significantly higher in women than in men (p < 0.05).

CONCLUSIONS

Lithium ratio does not appear to have a predictive role for thyroidal side effects of lithium therapy. Female gender was the main risk factor. We suggest more frequent thyroid evaluation of bipolar women who are treated with lithium.

Seasonal variations of lithium plasma levels

The aim of this study was to investigate the seasonal time course of lithium blood levels. We analyzed lithium plasma and red blood cell (RBC) levels in 186 subjects affected by bipolar (n=134) and major depressive (n=52) disorder, with stable oral dosage, followed in our lithium clinic for an average of 36 months. We observed a significant elevation of lithium plasma levels in summer with a more marked variation among early-onset subjects, bipolar subtype, and females. Lithium levels in plasma peaked in summer, and levels in RBC showed a trend in the same direction. Possible stratification factors such as presence of affected relatives or psychotic features did not significantly influence results. In conclusion, we observed a significant variation of lithium plasma levels according to seasons. If confirmed, this finding could have both clinical and research implications.

Lithium long-term treatment in mood disorders: clinical and genetic predictors

Lithium is the most widely used long-term treatment for recurrent mood disorders. Despite its proven efficacy, patients show a variable response, ranging from complete efficacy to no influence at all. This paper reviews possible predictors of response focusing on molecular genetic studies. The functional polymorphism in the upstream regulatory region of the serotonin transporter gene (5-HTTLPR) has been associated with lithium long-term efficacy in two independent studies, marginal associations have been reported for tryptophan hydroxylase and inositol polyphosphate 1-phosphatase (INPP1). A number of other candidate genes and anonymous markers did not yield positive associations. Therefore, even though some positive results have been reported, no unequivocal susceptibility gene for lithium efficacy has been identified.

The lithium ratio and the incidence of side effects

1. During a prospective and outpatient study the correlation between the lithium ratio and the incidence of lithium side effects and type of comedications was studied in 51 Iranian bipolar patients by using new direct method of measuring erythrocyte lithium concentration. 2. Results revealed that patients who received lithium alone the incidence of lithium side effects was extremely lower than those with lithium and neuroleptics in combination. Both neurological and renal side effects of lithium were higher in patients who received lithium in combination with neuroleptics. 3. In patients on lithium alone the lithium ratio among patients with side effects were significantly lower than those without side effects, and the plasma lithium concentrations were significantly higher in those with side effects. In patients who received neuroleptics in combination with lithium, the lithium ratios were also significantly lower in those with serious side effects than those with slight side effects, but there were no significant correlation in plasma lithium concentrations between them. 4. Previous studies about the correlation of the lithium ratio and incidence of side effects have yielded inconsistent results, and methodological problems may be a reason for these discrepancies. By using the new direct method of measuring erythrocyte lithium concentration, repetition of previous studies on lithium ratio may elucidate its value as a tool in daily practice.

The lithium index in a one-year follow-up

1. In a one-year follow-up 191 patients on lithium therapy, besides their regular check-ups, were assessed on mood, side-effects and intracellular lithium. 2. The authors were not able to find a correlation between the so called lithium index (i.e. the quotient intracellular lithium/plasma lithium) and the mood score. 3. In the group of patients which used no co-medication at all during the year of the follow-up the authors also failed to find a correlation between the lithium index and some of the clinically most relevant side-effects. However, in that selected group of "only-lithium-using-patients"-only 29 in all-the authors found a remarkable stability in the index value. 4. So even if the authors, in fact, rejected the lithium index estimation as a tool in daily praxis, the authors would once again underline the interesting findings about the so-called lithium index.