Yep. The body is not independent of the brain. Your other organs and especially the hormones they produce absolutely affect it.

But the brain is still not “just another organ”. The brain is special, as evidenced by the fact that the body gives it a special blood barrier. The brain also is you, to a greater extent than any other organ. This is why your thyroid can be removed and with appropriate hormone replacement, you’re mostly unaffected. No amount of hormones will replace the loss of your brain.

Also these psychological changes happen because these hormones ultimately go on to affect the brain

Except that non/under-functioning thyroid can usually easily and cheaply be replaced with levothyroxin. Anyone who feels that they’ve slowly been getting more tired and just can’t stop gaining weight should ask their doctor to get their T3 and T4 levels checked.

Finding out mine was underfunctioning and getting the levothyroxin dosage right made a ton of difference in my energy levels and stopped (but didn’t reverse) my weight gain.