Vitamin B12 Deficiency Overview - B12 deficiency affects the hormones
The human body is fascinating. Not only do we have the chemicals at the end of nerves, to transmit the signal from one nerve to the next (over very short distances, for speed), but we also have hormones which go around the whole body.
The brain talks to the thalamus and says "get ready for action" (very short signal). The thalamus sends a message to the hypothalamus "action needed for the next few minutes". The hypothalamus says to the pituitary "going to need adrenalin and testosterone at such and such a level" and the pituitary checks current levels in the blood and if it's too low, sends a signal to the endocrine organs to produce more of the needed hormones.
The pituitary keeps the hormones in the blood at the required levels, whilst periodically checking up the chain back to the brain to make sure they are needed.
Oh, and the thalamus and hypothalamus work on regular hormones too - growth hormones to manage the right amount of growth, sex hormones to change the body at the right times, monthly cycles, daily cycles.
Put simply, there's a lot to go wrong.
When you are hit with B12 deficiency, the likely damaged part in this whole chain of affairs is the pituitary. It has proteins poking through the membrane of the cells that are bathed in blood rushing past, which sample for levels of each hormone. If the membrane is damaged (as it often is with B12 deficiency) then the protein probes will be pointing in the wrong direction. This usually means that they report back that there's enough hormone in the blood even when there might not be, so mostly people are hypo- or under producing. It can happen the other way, where the pituitary thinks that there's more than there actually is.
Let's look at a couple of common examples:
low levels of thyroid hormone lead to low energy and stunted growth. Low levels can be caused either because the thyroid gland isn't able to produce enough thyroxine even though it's being told to produce more (with TSH - or Thyroid Stimulating Hormone) - known as Primary hypothyroidism, or because the signal from the pituitary gland never comes, so the thyroid gland is doing what it should but there's no signal to produce the amount the body needs - known as Secondary hypothyroidism.
Primary hypothyroidism can be caused by a number of factors and it's rarely anything to do with B12 deficiency.
So we're mainly concerned with a diagnosis of secondary hypothyroidism or low TSH but normal thyroid response to stimulation. This is where B12 can help.
Hypoadrenalism or Adrenal Insufficiency
The adrenal cortex produces Cortisol, the daily cycle hormone. This is the one that wakes you up in the morning and lets you sleep at night. Low cortisol can leave you constantly tired and yet unable to get to sleep because you haven't done anything all day.
Again, primary hypoadrenalism (the adrenal cortex inability to produce cortisol when the pituitary gland tells it to) is caused by some diseases and some auto-immune conditions. We're more interested in secondary hypoadrenalism where the ACTH isn't being produced but when it is produced, the adrenal cortex responds normally by producing cortisol.