Classification
There are several diseases where joint pain is primary, and is considered the main feature. Generally when a person has "arthritis" it means that they have one of these diseases, which include:

Osteoarthritis
Rheumatoid arthritis
Gout and pseudo-gout
Septic arthritis
Ankylosing spondylitis
Juvenile idiopathic arthritis
Stills disease
Psoriatic arthritisJoint pain can also be a symptom of other diseases. In this case, the arthritis is considered to be secondary to the main disease; these include:

Psoriasis
Reactive arthritis
Ehlers–Danlos syndrome
Iron overload
Hepatitis
Lyme disease
Sjögrens disease
Hashimotos thyroiditis
Celiac disease
Non-celiac gluten sensitivity
Inflammatory bowel disease (including Crohns disease and ulcerative colitis)
Henoch–Schönlein purpura
Hyperimmunoglobulinemia D with recurrent fever
Sarcoidosis
Whipples disease
TNF receptor associated periodic syndrome
Granulomatosis with polyangiitis (and many other vasculitis syndromes)
Familial Mediterranean fever
Systemic lupus erythematosus
An undifferentiated arthritis is an arthritis that does not fit into well-known clinical disease categories, possibly being an early stage of a definite rheumatic disease. Signs and symptoms
Pain, which can vary in severity, is a common symptom in virtually all types of arthritis. Other symptoms include swelling, joint stiffness, redness, and aching around the joint(s). Arthritic disorders like lupus and rheumatoid arthritis can affect other organs in the body, leading to a variety of symptoms. Symptoms may include:
Inability to use the hand or walk
Stiffness in one or more joints
Rash or itch
Malaise and fatigue
Weight loss
Poor sleep
Muscle aches and pains
Tenderness
Difficulty moving the jointIt is common in advanced arthritis for significant secondary changes to occur.
Factors that affect libido
Endogenous compounds
Libido is governed primarily by activity in the mesolimbic dopamine pathway (ventral tegmental area and nucleus accumbens). Consequently, dopamine and related trace amines (primarily phenethylamine) that modulate dopamine neurotransmission play a critical role in regulating libido.Other neurotransmitters, neuropeptides, and sex hormones that affect sex drive by modulating activity in or acting upon this pathway include:

Testosterone (directly correlated) – and other androgens
Estrogen (directly correlated) – and related female sex hormones
Progesterone (inversely correlated)
Oxytocin (directly correlated)
Serotonin (inversely correlated)
Norepinephrine (directly correlated)
Acetylcholine

Sex hormone levels and the menstrual cycle
A womans desire for sex is correlated to her menstrual cycle, with many women experiencing a heightened sexual desire in the several days immediately before ovulation, which is her peak fertility period, which normally occurs two days before and until two days after the ovulation. This cycle has been associated with changes in a womans testosterone levels during the menstrual cycle. According to Gabrielle Lichterman, testosterone levels have a direct impact on a womans interest in sex. According to her, testosterone levels rise gradually from about the 24th day of a womans menstrual cycle until ovulation on about the 14th day of the next cycle, and during this period the womans desire for sex increases consistently. The 13th day is generally the day with the highest testosterone levels. In the week following ovulation, the testosterone level is the lowest and as a result women will experience less interest in sex.Also, during the week following ovulation, progesterone levels increase, resulting in a woman experiencing difficulty achieving orgasm.