Sports Medicine: Just the Facts

182 SECTION 3 • MEDICAL PROBLEMS IN THE ATHLETE

ENDOCRINE GLANDS

• Anterior/posterior pituitary
  •Adrenal (cortex, medulla)
  •Thyroid
  •Pancreas
  •Parathyroid


• Gonadal

ANTERIORPITUITARYHORMONES ANDEXERCISE
(TABLE32-1)

A. Growth Hormone

• Endurance exercise:Magnitude of increased secre-
  tion related to both duration and intensity of exercise
  (Felsing et al, 1992)
  
  
  • Exercise must be at least 10 min in duration.
  
  
  • Many studies suggest exercise must be above lactate
    threshold for greatest growth hormone(GH) stimu-
    lus (Godfrey et al, 2003; Vanhelder et al, 1984).
  
  
  • Suggests a linear relationship between acute GH
    release and exercise intensity.
  
  
  
  

•Following a single bout of exercise, GH release tran-

siently decreases; 24 h GH is not elevated by single

bout.

• Possible mechanisms for increased secretion include
  the following:
  1.Increased sympathetic outflow (Weltman et al, 2000)
  2. Hypoxia (Vanhelder et al, 1984)
  3. Exercise-released endorphin has inhibitory effect
  on somatostatin (Borer et al, 1986).


• Resistance exercise: Increased GH secretion may be
  related to load, frequency, and rest intervals (Godfrey
  et al, 2003).
  
  
  1. Kraemer et al (1991) reported significant increases
     in GH when utilizing a 10-repetition maximum
     (10-RM), 1-min rest interval versus 5-RM with a
     3-min rest protocol.
  
  
  2. Higher volumes of resistance training (single set
     vs. multiple set) results in a significant increase in
     GH levels during recovery phase.
  
  
  
  


• Greater demands on anaerobic glycolysis appear to have
  more profound effect on GH release (Kraemer et al,
  1993).

TABLE 32-1 Anterior Pituitary Hormones

GLAND HORMONE CONTROL ACTION ENDURANCE RESISTANCE CHRONIC

Anterior Growth (GH) Hypothalamus;stimulated Promotes growth; Increased Increased Remains
pituitary by GHRH; inhibited by glucose sparing Glucose sparing Anabolic effects; controversial
somatos tatin; through (+) lipolysis, aids in endurance recovery through
Plasma levels of FFA and amino acid uptake, activities; depend- protein
glucose; feedback loops; (−) glucose uptake ent on intensity synthesis
pulsatile release
Thyrotropin Hypothalamus TRH Secretion of T3, T4; Conflicting Decreased Unknown
(TSH) Anterior Pituitary increases metabolism, Reserve energy
TSH Negative feedback lipolytic, (+) protein
loops via thyroid gland synthesis; increase HR,
contractility of heart
Corticotropin Hypothalamus (+) production and Increased Increased;during Conflicting
(ACTH) ACTH releasing hormone release of adrenal Glucose-sparing and throughout
(CRH) in response to hormones (cortisol, recovery; depen-
stress; negative aldosterone, sex dent on intensity
feedback via cortisol; steroids and the like); Increased
diurnal lipolytic
Follicular Hypothalamus (+) production of Conflicting No effect Conflicting;
Stimulating FSH, LH releasing estrogen, progesterone, Trained
Hormone hormone and testosterone Females may have
(FSH), Female lower resting
Lutenizing Estrogen, values dependent
Hormone Progesterone on menstrual stage;
(LH) Male Men’s values
Testosterone; remain unchanged
Pulsaltile
Prolactin Hypothalamus (+) milk secretion from Increased;higher Unknown May lower resting
(PRL) PRL releasing hormone; mammary glands in intensity values
PRL inhibiting hormone females; (−) testoster-
one; lipolytic
Endorphins Stress (−) pain; “exercise high” Increased; Lower levels needed;
duration Increase ex.
Dependent tolerance