Goliath was a giant that was over 9' tall according to 1 Samuel 17:4. If we are to believe the accounts of his size, he almost certainly had Acromegaly. Many of us have heard of Giants. People as tall as 9' tall still growing well after we would think a person had reached their full size. There is a disorder called Acromegaly that results in people becoming giants. It can be caused by different things, but ultimately, the pituitary gland secretes too much growth hormone which among other things causes the liver to continue making igf-1. Both of these substances cause people to grow, so too much of them can cause a person to grow too large.
black photo taking whiteOne of the most common causes of Acromegaly is a tumor on the pituitary gland that causes it to malfunction and release to much GH.
I saw a special on the discovery channel that argued that Goliath did in fact have Acromegaly. They also argued that he had a pituitary tumor and that was the cause of his Acromegaly. Now, if Goliath was really over 9' tall, I have no problem believing that he had Acromegaly, but I don't see anything in the passages that suggest other evidence supporting a tumor. There's certainly nothing that says he didn't have a tumor, but there's no reason to assume his Acromegaly was caused by a tumor.
First, let's decide if it's likely that Goliath did indeed have Acromegaly. If we accept the biblical passage that describes Goliath's height, he was six cubits and a span. A cubit is commonly converted to 18". A span is about 9". So six cubits and one span would be 117" or 9'9". I would think we can all agree this is not normal, and by any standard he would be giant. Since Acromegaly is the only thing I have found that explains people reaching heights of 9', I have no problem assuming he indeed suffered from the disorder.
That would also mean his hands would be unusually large, and his face would be elongated. He would indeed be very scary to see. That would support stories that claim the people of Isreal fled when they saw him. More than his extreme height, he would look and sound like a monster.
Was his Acromegaly caused by a tumor though? One of the other common problems caused by a pituitary tumor is that as it grows it presses against the optic nerve and causes visual problems and eventually blindness. Many people with this problem develop tunnel vision as the tumor grows. The special I saw today said that Goliath had tunnel vision and that fact supported the assumption that he had a pituitary tumor. I read 1 Samuel 16-18 but I didn't see anything that led me to believe he had tunnel vision.
The Discovery Channel Special said that this would explain why David was able to sneak up on him. Because Goliath had a defect in his peripheral vision, David was able to move on him by skirting around outside his normal vision, and get close enough to hit him with a stone. It also argued that this explained why a single rock was all it took to kill Goliath. If David snuck up beside him and hit Goliath in the side of the head, his large pituitary tumor would hemorrhage causing him to immediately faint, and quickly die. I have a couple of problems with this.