Treatment of nervous system disorders using combinations of RXR agonists and thyroid hormones

1. A method of treating Alzheimer's disease, the method comprising administering to an individual in need thereof a therapeutically effective amount of a RXR agonist and a thyroid hormone, wherein administration of the combination of the RXR agonist and the thyroid hormone treats the Alzheimer's disease in the individual, wherein the RXR agonist is 3,7-dimethyl-6(S),7(S)-methano,7-[1,1,4,4-tetramethyl-1,2,3,4-tetrahydronaphth-7-yl]2(E),4(E) heptadienoic acid, and has the structure of formula Ill:

and wherein the combination of RXR agonist and thyroid hormone causes a greater improvement in the Alzheimer's disease than the RXR agonist or thyroid hormone alone;

the method further comprising administration of a neurotrophic factor, or neurotrophic factor mimetic.

2. The method of claim 1 , wherein the neurotrophic factor is brain-derived neurotrophic factor (BDNF), glial-derived neurotrophic factor (GDNF), nerve growth factor (NGF), neurotrophin-3 (NT-3), fibroblast growth factor, basic (bFGF), ciliary neurotrophic factor (CNTF), neurotrophic factors-4/5 (NT-415), insulin-like growth factor (IGF), or insulin, or a mimetic of any one of these neurotrophic factors.

3. The method of claim 1 , wherein the neurotrophic factor is brain-derived neurotrophic factor (BDNF), glial-derived neurotrophic factor (GDNF), nerve growth factor (NGF), neurotrophin-3 (NT-3), fibroblast growth factor, basic (bFGF), ciliary neurotrophic factor (CNTF), neurotrophic factors-4/5 (NT-4/5), insulin-like growth factor (IGF), or insulin.

4. The method of claim 1 , wherein the neurotrophic factor is GDNF, or a GDNF mimetic.

5. The method of claim 1 , wherein the neurotrophic factor or neurotrophic factor mimetic is the neurotrophic factor.

6. The method of claim 4 , wherein the neurotrophic factor is GDNF.

7. The method according to claim 1 , wherein the combination of RXR agonist and thyroid hormone treats the Alzheimer's disease in the individual both by 1) promoting remyelination or neuroprotection of neurons and 2) modulating the individual's immune system.

8. The method according to claim 1 , wherein further combination with the neurotrophic factor promotes remyelination or neuroprotection.

9. The method according to claim 1 , wherein the therapeutically effective amount of the RXR agonist is about 0.001 mg/day to about 20 mg/day.

10. The method according to claim 1 , wherein the therapeutically effective amount of the RXR agonist is about 1 mg/day to about 10 mg/day.

11. The method according to claim 1 , wherein the thyroid hormone is thyroxine.

12. The method according to claim 11 , wherein the dose of thyroxine is about 12.5 μg/day to about 250 μg/day.

13. The method according to claim 1 , wherein the RXR agonist is administered directly to the central nervous system.

14. The method according to claim 1 , wherein the combination of RXR agonist and thyroid hormone is administered directly to the central nervous system.

15. The method according to claim 1 , wherein the combination of RXR agonist, thyroid hormone, and neurotrophic factor is administered directly to the central nervous system.

16. The method according to claim 1 , wherein the neurotrophic factor is administered directly to the central nervous system.

17. The method according to claim 1 , wherein the thyroid hormone is administered directly to the central nervous system.

18. The method according to claim 1 , wherein the RXR agonist is administered by nasal administration.

19. The method according to claim 1 , wherein the thyroid hormone is administered by nasal administration.

20. The method according to claim 1 , wherein the neurotrophic factor is administered by nasal administration.

21. The method according to claim 1 , wherein the combination of RXR agonist, thyroid hormone is administered by nasal administration.

22. The method according to claim 21 , wherein the neurotrophic factor is administered by nasal administration.

23. The method according to claim 1 , wherein the thyroid hormone is administered orally or subcutaneously.

24. The method according to claim 1 , wherein the RXR agonist is administered orally or subcutaneously.

25. The method according to claim 1 , wherein the neurotrophic factor is administered subcutaneously or intramuscularly.

26. The method according to claim 1 , wherein the neurotrophic factor is insulin.

27. The method according to claim 1 , wherein the neurotrophic factor is IGF.

28. The method according to claim 1 , wherein the neurotrophic factor is NGF.

29. The method according to claim 1 , wherein the neurotrophic factor is BDNF.

30. The method according to claim 1 , wherein treatment with the combination of RXR agonist and thyroid hormone reduces at least one symptom of Alzheimer's disease, wherein the at least one symptom reduced is mental decline, difficulty thinking and understanding, confusion in the evening hours, delusion, disorientation, forgetfulness, making things up, mental confusion, difficulty concentrating, inability to create new memories, inability to do simple math, inability to recognize common things, aggression, agitation, difficulty with self care, irritability, meaningless repetition of own words, personality changes, lack of restraint, wandering and getting lost, anger, apathy, general discontent, loneliness, mood swings, depression, hallucination, paranoia, loss of appetite, restlessness, inability to combine muscle movements, or jumbled speech.