Table 1. Effect of metformin given at the various age on age-related dynamics of estrous functional parameters in SHR mice.

Age, months	No. of mice		Length of estrous cycle, days	Rate of estrous cycles of various length, %			Fraction of mice with regular cycles, %
				< 5 days	5-7 days	> 7 days
Control
3		30	6.9 ± 0.28	0	64	36	81
7		29	8.1 ± 0.46	0	44	56	56
11		36	7.5 ± 0.50	0	44	56	50
14-15		24	7.4 ± 0.56	0	71	29	29
18		23	8.1 ± 0.56	0	33	67	39
21		21	8.0 ± 0.49	0	25	75	19
Metformin, 3 months
3		33	7.1 ± 0.26	0	64	36	92
7		32	6.5 ± 0.24 **	3	74 *	23 *	92,5 ***
11		30	6.2 ± 0.31 *	27	50	23 *	84 **
14-15		24	6.4 ± 0.34	3,7	81,5	14,8	87 **
18		20	7.7 ± 0.52	0	40	60	50
21		14	6.5 ± 0.37 *	0	75	25	43
Metformin, 9 months
11		32	6.1 ± 0.30 *	22	56	22 *	80 **
14-15		29	6.6 ± 0.32	7	76	17	81**
18		22	7.7 ± 0.41	0	50	50	50
21		12	7.7 ± 1.37	0	67	33	25
Metformin, 15 months
18		19	7.6 ± 0.37	0	50	50	42
21		13	6.4 ± 0.50 *	0	87 *	13 *	54*

The difference with the controls of corresponding age is significant: * p < 0.05; ** p < 0.01; *** p < 0.001.