## 2 Results
### The Effect of TP4/2 on the AC Activity in Thyroid Membranes and the Thyroid Hormones Levels
In the aging and diabetic rats, as in the young adult series, the ratio of the stimulating effects of TP4/2 and hCG on the blood TP levels was increased during their five-day administration (Figure 3E). In the aging and diabetic rats, the stimulating effects of hCG and TP4/2 on the content of 17-hydroxyprogesterone and T in the testes were lower than in the young adult groups, and in the diabetic rats the stimulating effects of hCG and TP4/2 on the content androstenedione were reduced (Table 2). The intratesticular T content in the Diab+hCG and Diab+TP groups was similar, and the difference in intratesticular T content between the Aging+hCG and Aging+TP groups was weak (Table 2) and correlated well with the blood T levels (Figure 3B). Quite unexpected was the accumulation of progesterone in the aging series, especially in the group Aging+hCG (Table 2). The Effect of Five-Day Treatment of Male Rats with TP4/2 and hCG on Intratesticular Expression of Genes Encoding LHCGR, StAR and Steriodogenic Enzymes  
In the testes of aging and diabetic animals, the expression of gene _Lhr_ encoding LHCGR tended to decrease, but the difference from the young adult rats was not significant (Figure 4). Five-day treatment of young adult rats with TP4/2 led to an increase in the _Lhr_ expression and did not affect this expression in the groups Aging+TP and Diab+TP. At the same time, hCG induced a decrease in the _Lhr_ expression in all the studied groups, to the greatest extent in T1 DM (Figure 4). Figure 4: Cont. Furthermore, the gene expression of StAR and four main steroidogenic enzymes catalyzing the synthesis of pregnolone (cytochrome P450\({}_{\text{scc}}\), CYP11A1, gene _Cyp11a_), progesterone (3\(\beta\)-hydroxy steroid dehydrogenase, gene _Hsd3b_), 17-hydroxy progesterone, androstenedione (cytochrome P450 17A1/steroid 17\(\alpha\)-monooxygenase, CYP17A1, gene _Cyp17a_), and testosterone (3\(\beta\)-hydroxy steroid dehydrogenase, gene _Hsd17b_) (for more details, see Figure S1) was studied. In aging and T1 DM animals, the basal expression of genes encoding steroidogenic proteins did not change significantly (Figure 4). In young adult animals, five-day treatment with TP4/2 led to an increase in the _Star_ and _Cyp17a_ expression, while hCG significantly increased the expression of the _Star_, _Cyp11a_ and _Cyp17a_ (Figure 4). In aging and diabetic rats, the stimulating effects of TP4/2 and hCG on the _Star_ and _Cyp17a_ expression were decreased, except for TP4/2's stimulating effect on the _Star_ expression in diabetic rats (Figure 4). Meanwhile, hCG stimulating effect on the _Cyp11a_ expression was reduced only in T1 DM (Figure 4). The _Hsd3b_ gene expression was increased significantly in the groups Aging+hCG, Diab+TP and Diab+hCG, and the _Hsd17b_ gene expression was slightly increased in the group Diab+TP. In the young adult animals, TP4/2 and hCG did not affect the gene expression of both dehydrogenases (Figure 4). Figure 5: The morphology of the seminiferous tubules in the testis of young adult rats, and the effect of five-day treatment with TP4/2 and hCG. **A**—Young+dmso, **B**—Young+TP, C—Young+saline; **D**—Young+hCG. The histology of the rat testes was evaluated using the staining of the testis section with Ehrlich hematoxylin and Eosin G. Scale bars, 100 μm. Figure 6: The morphology of the seminiferous tubules in the testis of aging rats, and the effect of a five-day treatment with TP4/2 and hCG. **A**—Aging+dmso, **B**—Aging+TP, C—Aging+saline, **D**—Aging+hCG. The histology of the rat testis was evaluated using the staining of the testis section with Ehrlich hematoxylin and Eosin G. Scale bars, 100 μm.