Yes, I apologize. I edited my post to correct that part.

Yes, there are pituitary conditions that can cause it to misbehave but then the T4/TSH lab findings would be different. Also hypothalamus which controls the pituitary. Also, T3 is important (and more potent). Some problems can occur "downstream" from the glands, where the T4/T3 conversion is "broken". This is why it is useful to get a full thyroid panels if the basic tests show something consistently off. Transient high or low levels of anything are possible, and not significant if retesting does not confirm them.

I found these links interesting... I liked the explanation in the first one:

http://fitsweb.uchc.edu/student/selectives/Luzietti/Thyroid_hormones.htm

Quote:

One can imagine the thyroid gland as a furnace and the pituitary gland as the thermostat. Thyroid hormones are like heat. When the heat gets back to the thermostat, it turns the thermostat off. As the room cools (the thyroid hormone levels drop), the thermostat turns back on (TSH increases) and the furnace produces more heat (thyroid hormones). The pituitary gland itself is regulated by another gland, known as the hypothalamus (shown in our picture in light blue). The hypothalamus is part of the brain and produces TSH Releasing Hormone (TRH) which tells the pituitary gland to stimulate the thyroid gland (release TSH). One might imagine the hypothalamus as the person who regulates the thermostat since it tells the pituitary gland at what level the thyroid should be set.

The second is a little over my head but perhaps useful. It reminds us that we need enough iodine:
http://fitsweb.uchc.edu/student/sele...d_hormones.htm