Q. When would you consider pubertal development as precocious ?
A. There are variations in the onset of puberty in various parts of the word. It is generally considered precocious when any of the sex characteristics appear before the age of 8 year in girls and 9 years in boys. Menarche before the age of 10 years is also precocious.
Q. What are the various forms of precocious sexual development? How do you classify ?
A. Puberty can occur prematurely due to early activation of the hypothalamic-pituitary-gonadal(HPG) axis or due to underlying pathologic conditions involving the gonads, adrenals or ectopic sites. When the HPG axis is activated it is known as central or gonadotropin dependent true
precocious puberty (CPP or TPP). Peripheral or pseudo precocious puberty (PPP) is gonadotropin independent. Here the pubertal development is partial or incomplete. CPP may be idiopathic or due to various CNS lesions. It is isosexual with complete physical and sexual maturation and establishment of reproductive gonadal function. Individual differences exist in its rate of progression. PPP can be iso or heterosexual, with only some of the sexual characteristics appearing early.
Occasionally CPP supervenes over PPP when the advanced state of skeletal maturation and the elevated sex steroid levels due to adrenal (e.g. CAH) or gonadal (ovarian cyst.) pathology provoke early maturation of the hypothalamic pituitary axis.
Besides these, there are conditions referred to as
variants of pubertal development, which include premature thelarche (PT), and premature adrenarche (PA) or rarely premature menarche. These are more commonly encountered in girls and occur as isolated unsustained non-progressive phenomena. Linear growth and skeletal maturation are not usually advanced. This group of children require careful periodic observation as these isolated phenomena may occasionally herald the onset of CPP/TPP. Complete work up and intervention may become necessary in the event of further progression.
Central Precocious Puberty (CPP) or True Precocious Puberty (TPP)Q.
What causes CPP/TPP ?
A. CPP occurs as an extreme variation of normal due to early HPG axis activation which may be idiopathic or it may be related to neurogenic causes with a spectrum of CNS lesions. In these instances, there is a premature decrease in the sensitivity of the gonadostat. In true precocity, the sexual maturation, growth spurt and advanced bone age are associated with pubertal levels of estrogens or androgens variable rise in the levels of gonadotropins. Increased rate of ossification results in early closure of epiphyses.
Q. Are there any
specific sex differences as regards CPP ?
A. True or central precocious puberty is more common in females and the idiopathic form accounts for over 80% of cases in females but only 40% males. Organic causes involving the CNS are important in boys. Overall it is 10 fold more common in girls than boys.
Q. Which is the commonest CNS lesion causing CPP ?
A. In our country, TBM or other inflammatory lesion of CNS are important. With availability CT and MRI, underlying lesions like hypothalamic hamartomas are detected in patients who would have been diagnosed as idiopathic CPP in the past. Hamartoma is a nonprogressive hypothalamic development malformation, which constitutes an ectopic site for the production of gonadotropin releasing hormone (GnRH) that influences gonadotropin secretion. This abnormality may be associated with seizure disorders, especially gelastic epilepsy and occasionally with variable degrees of mental subnormality.
Q. Are there any
other causes of precocious sexual development ?
A. One of the most intriguing complexes is the unusual syndrome of sexual precocity associated with juvenile hypothyroidism. This is the only form of sexual precocity where growth is arrested rather than stimulated. McCune Albright Syndrome may also be associated with CPP but frequently PPP due to ovarian cysts. A syndrome of gonadotropin independent precocious puberty resembling the true from has now been identified as occurring more frequently in males (familial testotoxicosis) and probably accounts for some of the familial forms of CPP reported in the past. The inheritance is sex limited autosomal dominant. Tumors like hepatoblastoma or teratoma may also produce CPP by releasing GnRH. Drugs or accidental ingestion of hormone containing pills, inadvertent use of anabolic steroids, food or vitamins contaminated with artificial estrogens, foreign body or tumors of the genital tract are some of the other causes which may cause confusion.