Nelson's syndrome



Nelson's syndrome

Nelson's syndrome is the rapid enlargement of a pituitary adenoma that occurs after the removal of both adrenal glands

Pathophysiology:

Removal of both adrenal glands, or bilateral adrenalectomy, is an operation for Cushing's syndrome. Removal of both adrenals eliminates production of cortisol, and the lack of cortisol's negative feedback can allow any preexisting pituitary adenoma to grow unchecked. Continued growth can cause mass effects due to physical compression of brain tissue, along with increased production of adrenocorticotrophic hormone(ACTH) and melanocyte stimulating hormone (MSH).

Clinical Presentation:

The common signs and symptoms include muscle weakness and skin hyperpigmentation due to excess MSH. Nelson's syndrome is now rare because bilateral adrenalectomy is now only used in extreme circumstances.

Management:

Pituitary surgery is performed in some cases. The risk can also be minimized by pituitary irradiation.

Kallmann syndrome

Kallmann syndrome is a hypogonadism (decreased functioning of the glands that produce sex hormones) caused by a deficiency of gonadotropin-releasing hormone (GnRH), which is created by the hypothalamus. Kallmann syndrome is also called hypothalamic hypogonadism, familial hypogonadism with anosmia, and hypogonadotropic hypogonadism, reflecting its disease mechanism.

Kallmann syndrome is a form of tertiary hypogonadism, reflecting that the primary cause of the defect in sex-hormone production lies within the hypothalamus rather than a defect of the pituitary (secondary hypogonadism), testes or ovaries (primary hypogonadism).

Kallmann syndrome was described in 1944 by Franz Josef Kallmann, a German-Americangeneticist. However, others, such as the Spanish doctor Aureliano Maestre de San Juan in 1856, had noticed a correlation between anosmia and hypogonadism.

Clinical Features:

Kallmann syndrome's characteristics:

Hypogonadotropic hypogonadism (a lack of the pituitary hormones LH and FSH)

Congenital (present from birth) anosmia (complete inability to smell) or hyposmia (decreased ability to smell)

Normal stature

It can occasionally be associated with optic problems, such as colour blindness or optic atrophy, nerve deafness, cleft palate,cryptorchidism, renal agenesis, and mirror movement disorder. However, it is not clear how, if at all, these other problems have the same cause as the hypogonadism and anosmia.

Males present with delayed puberty and may have micropenis (although congenital micropenis is not present in most male KS cases).

Females present with delayed puberty (i.e., primary amenorrhea) and lack of secondary sex characteristics, such as breast development.

A fraction of cases may present with post-pubertal onset, which results in a phenotypically normal penis in men with subsequent testicular atrophy and loss of some secondary sex traits. These men generally present with sexual impairment and low libido. In women, late-onset Kallmann Syndrome can result in secondary amenorrhea. Anosmia may or may not be present in these individuals.

Physical findings associated with hypogonadism include eunuchoidal skeletal proportions.

A low ratio, less than 1:1 in adults, of the upper body segment (crown to pubis) to the lower body segment (pubis to heels) is present only in patients with classic Kallmann syndrome or idiopathic hypogonadotropic hypogonadism.

Similarly, an arm span greater than height by more than 5 cm is observed only in patients with congenital Kallmann syndrome or idiopathic hypogonadotropic hypogonadism.

Height for age is normal in these patients, distinguishing them during adolescence from individuals with constitutional delay in growth and development because adolescents in the latter group tend to be short for chronological age.

Absence of terminal facial hair and decreased body hair is observed in men with Kallmann syndrome or who have congenital idiopathic hypogonadotropic hypogonadism. Men with adult-onset idiopathic hypogonadotropic hypogonadism may report decreased shaving frequency. In addition, lack of temporal hair recession (male-type baldness) is noted in men with Kallmann syndrome or idiopathic hypogonadotropic hypogonadism.

High-pitched voice is present only in men with Kallmann syndrome or congenital idiopathic hypogonadotropic hypogonadism.

Lack of breast development is observed in women with Kallmann syndrome or congenital idiopathic hypogonadotropic hypogonadism. Women with long-standing hypothalamic amenorrhea may experience a decrease in breast size.

Gynecomastia is observed only rarely in men with classic Kallmann syndrome or idiopathic hypogonadotropic hypogonadism at the time of diagnosis, but it may occur as an adverse effect of androgen replacement therapy in these patients.

Muscle mass is decreased, muscle strength is diminished, and fat is distributed over the hips and chest, particularly in men with Kallmann syndrome or congenital idiopathic hypogonadotropic hypogonadism.

Axillary and pubic terminal hair may be scantly present in these patients (with the exception of patients with X-linked idiopathic hypogonadotropic hypogonadism and AHC) because of circulating adrenal androgens. Males with Kallmann syndrome or congenital idiopathic hypogonadotropic hypogonadism lack terminal hair growth along the midline towards the umbilicus.

Men with Kallmann syndrome or congenital idiopathic hypogonadotropic hypogonadism have prepubertal testes (30 mEq/L), and decreased serum osmolality. These findings occur in the absence of diuretic therapy; in the presence of euvolemia without edema; in the setting of otherwise normal cardiac, renal, adrenal, hepatic, and thyroid function; and in absence of factors known to stimulate ADH secretion such as severe pain, hypotension, and stress.

In SIADH, the inappropriately elevated level of vasopressin enhances the reabsorption of water, thus concentrating the urine. It is the excess free water absorption that causes hyponatremia.

Two scenarios can occur in which vasopressin secretion will be not be correlated with the serum osmolality. First, a decrease in the effective circulatory volume may be falsely sensed by the large arterial baroreceptors in conditions such as cirrhosis, nephrotic syndrome, and congestive heart failure. In these cases, the stimulus for ADH secretion overrides osmotic signals, which are conveying a hypoosmotic state. ADH secretion ensues despite hypoosmolality resulting in hyponatremia. In contrast to patients with SIADH, these patients appear hypervolemic.

Second, inappropriate ADH secretion occurs when there is dysregulation of cells secreting vasopressin or in the feedback mechanisms responsible for its release. A variety of ADH-secreting tumors both inside and outside the pituitary have been associated with SIADH, as well as certain CNS disorders, pulmonary disorders, and medications (see Differentials).

A distinction should be made between the SIADH and the clinical syndrome of euvolemic hyponatremia. A mutation of the ADH receptor can make it more responsive to ADH and can result in the same clinical picture of hyponatremia, concentrated urine output, and decreased serum osmolality but with normal ADH secretion.

Clinical Findings:

In general, increased ADH causes water retention and extracellular fluid volume expansion without edema or hypertension, owing tonatriuresis (the excretion of sodium by the kidneys). The water retention and sodium loss both cause hyponatremia, which is a key feature in SIADH. Hyponatremia and concentrated urine (UOsm >300 mOsm) are seen, as well as no signs of edema or dehydration. When hyponatremia is severe (sodium ................
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