Obesity
Obsessive compulsive disorder (OCD)
Obstipation
Obstruction of duodenum
Occlusive arterial disease
Oligomenorrhoea
Oligospermia
Oophoritis
Ophthalmoplegia, progressive external
Optic atrophy
Oral aphthae, recurrent
Oral candidiasis
Oral cavity cancer
Oral leukoplakia
Oral lichen planus
Orchitis
Orthostatic hypotension
Osteoarthritis

Osteoarthritis of lumbar disk
Osteoarthritis of the knee
Osteochondromas
Osteoclastoma
Osteomalacia
Osteomyelitis
Osteonecrosis of femur
Osteoporosis
Osteosarcoma
Otitis media, chronic secretory
Ototoxic hearing loss
Ovarian cancer
Ovarian pregnancy
Ovarian tumor, benign
Overlap syndrome
Overweight
Ovulation bleeding
Ozostomia