Diseases associated with the hypothalamus and the hypothalamic pathway

Because the hypothalamus has so many connections to other parts of the brain and body any genetic defects or lesions to even a single neuron could have a substantial effect on the endocrine/ autonomic nervous sytem of oneself.

Diseases concerned with hormonal function could subsequently occur as a result of hypothalamic or pituitary gland defects due to the tight integration of both these structures. However specific tests on hormones can be done to distinguish which is mainly responsible for the dysfunction.

Neurogenic diabetes insipidus

This occurs due to a lack lack of vasopressin hormone production from the brain. Ultimately if the hypothalamus is the main cause of this disease there would be a defect with the expression of vasopressin from the periventricular and supraoptic nuclei. This damage to the hypothalamus which produces the hormone (or pituitary gland which secretes it) may have occured due to head trauma thus causing a decrease of this hormone within the subejct's system.

Obesity

Recent studies show that in some cases the underlying cause of obesity may be down to a genetic defect of a hormone called leptin. The hormone leptin which is secreted from fat cells into the blood stream increases in concentration and the orexigenic neurons in the lateral hypothalamus are no longer stimulated to signal the feeling of hunger. At the same time the arcuate neurons located in the periventricular zone signal the feeling of being full and hence causes an increase in metabolism. The gene which codes for this hormone 'OB', may be defective in those who are diagnosed as clinically obese. Hence fat cells are unable to release the peptide hormone into the blood stream and signal to the satiety centre to decrease appetite when somebody has eaten enough. This leads to overeating and an increase in weight over time.

Horner's Syndrome 

Is caused by a deficiency of the sympathetic Nervous system. The hypothalamus plays a role as a 'first order neuron disorder' involving the hypothalamospinal pathway. This deficiency in sympathetic innervation would be caused by a lesion somewhere in the pathway hypothalamospinal pathway as well as other pathways incorporated in the sympathetic nervous system. Symptoms of this syndrome include: drooping of the eyelid, blood shot conjunctiva, flushing of the affected side of the face.

Children who are born with this defect are often born with heterochromia due to there not being a sufficient amount of sympathetic innervation interfering with melanin pigmentation of melanocytes in the superficial stroma of the iris.

Photo showing a woman who suffers from Horner's syndrome where the woman's left eye has been affected: Image courtey of wiki-commons.

Kallman Syndrome

Causes hypogonadism where the secretion of testosterone in males and oestrogen in females is below normal. This ultimately is a result of a deficiency of the hormone GnRH. It is a form of secondary hypogonadism as primary hypogonadism is due to a defect effecting the actual gonads.

The underlying cause of Kallman's syndrome occurs during development where there is a defect of the GnRH neurons not able to migrate properly from the olfactory placode during development to the hypothalamus. this also interferes with the development of the olfactory bulb leading to anosmia as a result of potential hypoplasia of these cells failing to migrate.

Because the production of GnRH is low in people with Kallman's syndrome the pituitary doesn't produce enough gonadotrophin's from the adenohypophysis

Characteristics of sufferer's form this disease will mainly have problems with developing secondary sex characteristics.

Diagram illustrating the different hormones secreted from the hypothalamus and their destination within the body. Image courtesy of: commons.wikimedia.org/wiki/File:Hormones_feedback.png

Hypothyroidism

 Is where the thyroid gland is underactive thus the levels of thyroxine are below normal and results in a decreased metabolism. Sufferers of hypothyroidism's bodily functions (involving cells and tissues) occur at a much slower pace. There are three types of hypothyroidism depending on the origin from which the defect lies among the TSH pathway. Tertiary hypothyroidism occurs as a result in the defect lying within the hypothalamus. In this case the hypothalamus does not produce sufficient amounts of TRH and so the pituitary gland cannot be stimulated to produce TSH. 

Symptoms of those suffering from hypothyroidism include: cold, intolerance, fatigue, dry flaky skin and weight gain. to determine diagnosis of this disease a blood test is required.

Below is a video of a doctor describing the differences in Chronic fatigue and hypothyroidism: