Metandienone Wikipedia
Electronegative atoms in a heteroaromatic ring withdraw electron density from the π‑system by inductive effect.
Because the aromatic ring is now poorer in electrons, it becomes deactivated toward electrophilic attack – the σ‑complex that is formed during an EAS reaction is less stable.
The withdrawal of electron density also makes the positions on the ring that are directly attached to the heteroatom (or next to it) even poorer in electron density.
Consequently, https://www.valley.md/dianabol-cycle-benefits-and-risks the most favourable site for an electrophile is usually a position that is farther from the heteroatom – often the para‑like or meta‑like position relative to the heteroatom.
In short: inductive withdrawal deactivates the ring and shifts the reactivity toward positions further away (often para) from the electron‑withdrawing heteroatom.