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Pediatrics - Abnormal Pubertal Development
Whiteboard Animation Transcript
with Paola Luca, MD
medskl.com/module/index/abnor...
Puberty is the normal and expected transition from childhood to adolescence and involves both physiological and psychosocial factors. Normal pubertal development begins with maturation of the hypothalamic-pituitary-gonadal (HPG) axis. Pulsatile release of gonadotropin-releasing hormone (GnRH) stimulates release of the hormones luteinizing hormone (LH) and follicle-stimulating hormone (FSH) which induce the maturation of the gonads. Subsequent production of sex steroids begins the development of secondary sexual characteristics.
Abnormalities in pubertal development are discussed from the delayed and precocious perspectives.
Delayed puberty is defined as failure to develop secondary sexual characteristics by 2 standard deviations (95%) from the mean i.e in males a lack of testicular development (the first sign of puberty in boys) by age 14, and in females a lack of breast development (the first sign of puberty in girls) by age 12. Causes of delayed puberty can be divided into primary gonadal disorders (associated with high levels of LH and FSH), either congenital (e.g. Turner and Kleinfelter syndromes) or acquired causes (e.g. gonadal trauma, infection, chemotherapy), and secondary gonadal disorders (associated with low or normal LH and FSH levels), either functional (e.g. constitutional delay of puberty, malnutrition, chronic illness, hyperprolactinemia, hypothyroidism), hypothalamic or pituitary dysfunction (e.g. central nervous system (CNS) tumor), or genetic causes (e.g. congenital GnRH deficiency with anosmia or Kallman syndrome)
Precocious puberty is defined as the development of secondary sexual characteristics before age 8 years in girls and before age 9 years in boys. Precocious puberty can be further classified into central and peripheral etiologies. Central precocious puberty is gonadotropin-dependent and is caused by premature activation of the HPG axis. Causes include CNS lesions (e.g. hamartomas, CNS tumors, CNS irradiation, hydrocephalus) and genetic mutations. Peripheral precocious puberty is gonadotropin-independent and stems from increased secretion of sex hormones. This can occur from the gonads (e.g. ovarian cysts, ovarian tumors, Leydig cell tumor of the testes), the adrenals (e.g. tumors, untreated congenital adrenal hyperplasia), ectopic human chorionic gonadotropin (hCG) production by a germ cell tumor, or exogenous sex hormone exposure. Primary hypothyroidism and McCune-Albright syndrome are also causes of peripheral precocious puberty.
Evaluation of delayed or precocious puberty should always start with a thorough medical history, family history and physical exam, including height, weight, height velocity, and Tanner staging of pubertal development. Investigations for delayed puberty generally include a bone age to assess skeletal maturation and blood work for LH, FSH, estradiol (females), testosterone (males), prolactin, thyroid-stimulating hormone (TSH) and free T4. Screening for chronic disease includes a complete blood count, erythrocyte sedimentation rate and liver function tests. Further investigations are dependent on initial results.
Investigations for precocious puberty include a bone age, LH, FSH, estradiol (females) and testosterone (males). Further testing may include brain MRI, ultrasound of the pelvis, adrenals or testicles, measuring LH levels after GnRH agonist stimulation, adrenal androgens, or hCG in boys.