The gonadotropin-induced activation of cAMP-independent signaling pathways is involved in the regulation of growth, differentiation, and cytoskeletal reorganization, as well as LHCHR desensitization in the target cells [6; 7]. The low-molecular-weight (LMW) agonists of LHCGR are possibly a good alternative to gonadotropins. Unlike LH and hCG, they bind to the allosteric site, which is localized inside the LHCGR transmembrane domain formed by seven hydrophobic helices [16; 17]. Of greatest interest among LHCGR allosteric agonists are the thieno[2;3-\(d\)]pyrimidine (TP) derivatives, which, as shown earlier by us and other authors, activate steroidogenesis in vitro and in vivo conditions [16; 18; 19; 20; 21; 22; 23]. The TP derivatives are more selective as the regulators of intracellular signaling in target cells in comparison with gonadotropins. The compound Org 43553 (Figure S2), discovered by Dutch scientists in 2002, and the compounds TP1 and TP3, developed by us, selectively activate the G\({}_{\text{s}}\) proteins and AC, but have a little effect on the G\({}_{\text{q}/11}\) proteins and intracellular calcium signaling [16; 24]. Dysfunctions in the hypothalamic-pituitary-gonadal axis, which are common in male patients with type 1 diabetes mellitus (T1 DM) and in older men, lead to an imbalance in steroid hormones, androgen deficiency and impaired spermatogenesis [25; 26; 27; 28; 29]. The main cause for this is the impaired steroidogenic response of the testes to gonadotropins [30]. It is shown that the gonadotropin stimulating effect on androgen production in T1 DM patients is reduced, especially in severe and moderate forms of this disease [28; 29; 31]. In turn, older men with increased LH levels often exhibit testicular resistance to gonadotropins and androgen deficiency [32; 33; 34]. In T1 DM and aging, a decrease in testicular sensitivity to LH and hCG may be due to both a decrease in the number of functionally active LHCGRs and impaired LH signaling in Leydig cells, as a result of increased oxidative stress, apoptosis and inflammation in the testes [30; 35]. Since the molecular mechanisms of interaction of allosteric agonists with LHCGR are significantly different from those of gonadotropins, we hypothesized that the effects of gonadotropins and TP derivatives on testicular steroidogenesis and spermatogenesis may also differ. This assumption is based on our early data that TP3 causes LHCGR desensitization to a much lesser extent in comparison with hCG [24; 36]. In addition, being hydrophobic substances, TP derivatives are able to penetrate into the cell, bind to the \"immature\" forms of LHCGR and facilitate their translocation into the plasma membrane, thereby functioning as LMW chaperones [37]. This is very important in the case of T1 DM and aging, where inflammation, oxidative stress and endoplasmic reticulum stress are triggered in the testes, and this leads to the damage of testicular proteins and impairs their post-translational modification and transport [38; 39; 40; 41]. Based on the above, the aim of our work was to carry out a comparative study of the effects of 5-amino-N-_tert_-butyl-4-(3-(1-methylpyrazole-4-carboxamido)phenyl)-2-(methylthio)thieno[2,3-_d_] pyrimidine-6-carboxylic acid amide (TP4/2) (Figure S2) and hCG on AC activity in testicular membranes in the in vitro conditions, as well as on testosterone (T) levels, testicular steroidogenesis and morphology of the seminiferous tubules in young adult (four-month-old), aging (18-month-old) and diabetic male Wistar rats with a five-day administration of these drugs. We have shown for the first time the significant differences between the steroidogenic effects of TP4/2, an allosteric agonist of LHCGR, and hCG, an orthosteric agonist of this receptor, with their single and long-term (five-day) administration.