What was wrong with Hitler's left hand?

Hitler began to contract Parkinsons disease in the last few years of war, explaining why his left hand shaked as it did,=.

According to his private Drs notes in a recent documentary he was showing signs of Parkinson's disease.. That's why he kept his hand behind his back often and had still photos taken not a lot of movies.

Come on guys!

Hitler having Parkinson's disease is a pure speculation. The film with Hitler's shaking hand behind his back was recorded on April 25. What happened right before that? Let's see the Wikipedia article on this: „On 20 April 1945, Morell, Albert Bormann, Admiral Karl-Jesko von Puttkamer, Dr. Hugo Blaschke, secretaries Johanna Wolf, Christa Schroeder, and several others were ordered by Hitler to leave the bunker and Berlin by aircraft for the Obersalzberg. Hitler told Morell he did not need any more medical help, although he continued to take many of the medications Morell has prescribed for him; during the last week of Hitler's life, it was administered by Dr. Werner Haase and by Heinz Linge, Hitler's valet. The group flew out of Berlin on different flights by aircraft of the Fliegerstaffel des Führers over the following three days. Morell was on the flight which left Berlin on 23 April.” So, Apr. 25 was the 5th or 2nd day of Hitler without stimulating drugs like amphetamine. His shaking hand isn't a sign of Parkinson's disease, but that of withdrawal symptoms.

Hitler was a hypochondriac, and received many "experimental" medications from his "doctors" (many of whom would be called quacks now, and then, were it not for their powerful protectors in the Nazi hierarchy).
Some of these contained mercury, a known neurotoxin, and other nasty things that will have caused neuromuscular problems.
Combined with stress, that's understood to be the main cause for his "tic". All this was mentioned in several programs on NGC and History a few years ago before both degenerated into conspiracy theory central, and I've read things about it as well in books over the years (maybe the (in)famous doctor's diaries have some information as well, never read them).

If we are leaving out the Parkinson's "diagnosis" something to consider that everyone has left out is that on July 20 1944 Hitler had nearly been killed in a bomb plot. This could have had effects on him physically and on his nerves when in basically the same situation.

It wasn't Parkinson's, it was a nervous tic. Why? Because he was losing the war and slowly breaking down. It all culminated in the famous meltdown scene that has been parodied so many times. Notice he loses the tic during that scene.

PS Downfall is just a movie. It is neither historical fact, nor a documentary.

If we consider Wikipedia a reliable source, especially on a sensitive topic and on a person like Adolf Hitler, there is no room for speculation, but only factual information.

Looking at the Wikipedia page for Adolf Hitler on the health section. We can be sure that if Ian Kershaw, one of the top historians about the Third Reich and Hitler, did not find any convincing evidence about Parkinson's disease. He believed he might have suffered from Parkinson's disease, which is what he wrote in his book, but he found no compelling evidence. He was able to remove fact from hearsay and speculation, which is what we should do.

A movie script, has the freedom to use the speculation and other wild stories to make the script more exciting, and to make you love/hate/understand the main character better.

From Wm. Shirer's 'The Rise and Fall of the Third Reich', which is sourced from diaries of various Nazi officers as well as the Reich's secret papers captured by the allied forces:

"The generals who assembled at the Führers headquarters at Ziegenberg on the evening of December 12th, minus their briefcases and revolvers, found the Nazi warlord, as Manteuffel later recalled, "a stooped figure with a pale and puffy face, hunched in his chair. His hands trembling, his left arm subject to a violent twitching which he did his best to conceal. A sick man... When he walked, he dragged one leg behind him."

Hitler's doctor noted in his diary on August of 1941 "Left hand shows a tremor." This first-hand account is likely the chief reason that they chose to include this in Downfall. But there is also film of Hitler where the tremor can be seen.

Several doctors (Dr. Tom Hutton and J. L. Morris chief among them) have concluded that Hitler must have been suffering from Parkinson's by, and likely before, 1941.

I'm going to take a stab at this because I also have Parkinson's Disease.

Parkinsonism is an umbrella term that describes many conditions which share some of the symptoms of Parkinson's. The main symptoms of Parkinson's – tremor, rigidity and slowness of movement – are also the main symptoms of a number of conditions that are grouped together under the term parkinsonism. Generally, Parkinson's symptoms are caused by a lack of dopamine in the brain. See more.

Yesterday (September 30, 2014), I attended a fascinating lecture by Dr. Abraham Lieberman, M.D., a neurologist who specializes in Parkinson's and has written and lectured extensively on his analysis of Hitler's handwriting, films of his speeches, still photographs, and reports of his behavior. I am rewriting this answer to include his analysis.

The most common form of Parkinson's is Idiopathic Parkinson's disease. Its typical symptoms are tremor, rigidity and slowness of movement, among others, but symptoms and the rate the condition progresses can vary in each patient. The underlying cause of idiopathic Parkinson's is unknown and a diagnosis is usually determined after testing the patient with anti-Parkinson's medicines, such as carbidopa/levodopa. Ibid. This medicine was not developoed until the 1960s and would not have been available to Hitler.

Parkinson's can also include a slow gait (which is how I was first diagnosed five years ago), stooped posture, a voice reduced to a whisper, and a dull stare that does not seem to focus on its surroundings. Those suffering from Parkinson's can also suffer from cognitive disorders that include a lack of imagination and spontaneity, difficulty making decisions and general apathy.

Lieberman believes that all evidence points to Hitler having Parkinson's, although some of his behavior may be explained by other factors. However, Lieberman believes that after being gassed in World War I, Hitler contracted encephalitis which was being transmitted at about the same time as the Spanish Flu, and that Hitler had the post-encephalitic brand of Parkinson's, rather than the more common idiopathetic type. One clue for this is that in Mein Kampf, Hitler tells that he had a "relapse" of symptoms he suffered during his gassing. This is extremely unlikely, Lieberman says, and was more likely a cover story to describe his hospitalization for von Economo's encephalitis -- something a rising politician would not want to admit. Hitler's asocial behavior; his obsessions and compulsions, his cruelty and rages can be explained by a diagnosis of von Economo's encephalitis. A. Lieberman, "Hitler Had Post-encephalitic Parkinsonism," Pubmed.com, National Institute of Health, Apr. 1996.

Lieberman says that Hitler may have shown transient Parkinson's symptoms as early 1923 when he was 34, possibly in his handwriting which is beginning to become smaller. Film of his speaking during the 1920s, however, show that he enthusiastically waved both arms during speeches. In contrast, by the mid 1930s, Hitler speaks with his left hand at his side or in a pocket. Where the left hand is shown in film, tremors can be seen. Looking at Hitler's handwriting from the 1920s, 1930s, 1943 and 1945, Lieberman demonstrated that there was a clear trend to micrography -- i.e. the signature becomes smaller and smaller. Photographs in 1945 show Hitler stooped over, his face lacks expression, and according to Albert Speer and others, Hitler dragged his left foot and spoke more softly.See this article.

A common symptom of Parkinson's is that patients show a lack of impulse control, often turning to gambling and other high-risk endeavors. Lieberman notes that even before he showed Parkinsonian symptoms, Hitler was a gambler -- his takeover of the German government, and his earlier attempt at a putsch, being prime examples. He said that while some scholars believe that Parkinson's affected Hitler's judgment, and his failure to take the advice of his generals, that is a difficult conclusion. Parkinson's may have enhanced his risk-taking nature, but one cannot conclude this based on available evidence. He writes of this in this paper.

Lieberman also questioned the conclusion of Prof. Nassir Ghaemeni who believed that Hitler abused amphetamines and was bipolar. Lieberman said in the lecture and in his papers that Ghaemeni could not conclude that based only on hearsay and without actually meeting Hitler in person.

In series Nazi Underworld (episode "Patient Hitler"), you can see original footage from a German propaganda film (that was censored at the time) with Hitler's left hand tremor. The authors claim that it was one of the symptoms of Parkinson's disease. Also they mention forward-flexed posture as another symptom. But they say there is no actual medical records about Parkinson's disease from Hitler's doctors, except perhaps the opinion of Professor Max de Crinis.

I found this also in Adolf Hitler's Parkinson's disease and an attempt to analyse his personality structure:

It has been proved that Adolf Hitler suffered from idiopathic Parkinson's disease. No indication for postencephalitic parkinsonism was found in the clinical symptoms or the case history. Professor Max de Crinis established his diagnosis of Parkinson's disease in Hitler early in 1945 and informed the SS leadership, who decided to initiate treatment with a specially prepared ‘antiparkinsonian mixture’ to be administered by a physician. However, Hitler never received the mixture, this implies that the SS intended to remove the severely diseased ‘Leader’.

Two different character traits can be analysed in Hitler's personality: on the one hand the typical premorbid personality of parkinsonian patients with uncorrectable mental rigidity, extreme inflexibility and insupportable pedantry. On the other an antisocial personality disorder with lack of ethical and social values, a deeply rooted tendency to betray others and to deceive himself and uncontrollable emotional reactions. This special combination in Hitler's personality resulted in the uncritical conviction of his mission and an enormous driving for recognition. The neuropsychiatric analysis of Hitler's personality could lead to a better explanation of the pathological traits of one of the most conspicuous historical personalities.

Yes, Hitler had a tremor of his left hand. According to F. Gerstenbrand, E. Karamat he had a Parkinson's disease.

The encyclopaedia, following Kershaw, Ian (2008). Hitler: A Biography. New York: W. W. Norton & Company p 782, claims Parkinsons. This is I believe the standard account.

Joachim Fest, who wrote a major Hitler biography in German, cites four sources and concludes thus (in footnote 63 on p. 807 of the English paperback edition):

Probably the exact nature of Hitler's illness can no longer be determined, since no examination with a specific investigatory aim was ever undertaken. Because of the extremely inadequate documentation, none of the various diagnoses can be persuasiverly supported or rejected; the principal symptom of both Parkinson's disease and the Parkinson syndrome, namely the shaking arm or leg, can also be caused by many other diseases.

The shaking of Hitler's left arm and the fact that he tried to hide it is also mentioned on several occasions in this biography.