Plasma total biopterin and tetrahydrobiopterin levels of 10 normal controls and 10 patients with monopolar depression were measured with and without internal standard. The levels did not differ between the two methods. A significant increase of total biopterin levels and the lower ratio of tetrahydrobiopterin to total biopterin in the depressive phase were observed in the plasma of patients with depression compared to normal controls, and these changes in plasma biopterin tended to normalize in the remission phase.

This paper studies changes in the concentrations of tetrahydrobiopterin (BH4), the cofactor of tyrosine hydroxylase, in blood under physical stress and in depression. BH4 was found to be transiently released from the sympathetic nerves under severe physical stress but continuously released in depression with an increased oxidation rate of BH4 to B.

Plasma total biopterin and tetrahydrobiopterin levels of 14 normal pregnant and 15 normal puerperal women (within 1 week after delivery) were measured. In the first group, total biopterin levels were already increased (average: 18.2 pmol/ml) in the second trimester and remained high until the early puerperal period. In the second trimester, the ratio of tetrahydrobiopterin to total biopterin levels decreased to 72.3% and even further to 66.1% in the third trimester. This tendency continued until the puerperal period. Compared with the control group (12 healthy nonpregnant women), total biopterin levels increased during pregnancy and the puerperal period (p < 0.001), and the ratio in the third trimester and the early puerperal period decreased (p < 0.001). The depressive state according to Zung’s score appeared most markedly in the third trimester with a mean score of 48, and tended to recover to a mean score of 36.2 in the early puerperal period. In this period, a correlation was found between Zung’s score and the total biopterin levels (r = 0.80), and the ratio of tetrahydrobiopterin levels to the total biopterin levels (r = –0.92). In the early puerperal period, total biopterin levels were higher in subjects with Zung’s scores ≧36 (p < 0.001); the ratios of this group were lower than those of subjects with Zung’s scores <36 (p < 0.001). Plasma biopterin levels in pregnancy and the early puerperal period closely resembled those of patients with mood disorders who show depressive symptoms from a psychoneurological perspective. Therefore, it seems possible that a depressive state in pregnancy and the early puerperal period has the same pathology as depression.

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